External pacing device with discomfort management

ABSTRACT

An external medical device includes at least one therapy electrode configured to be disposed on a patient; and a treatment manager configured to execute a baseline process to determine at least one of a range of values for a discomfort parameter and a patient discomfort threshold value corresponding to the at least one pacing routine, detect a cardiac condition of the patient, execute the at least one pacing routine, the at least one pacing routine being associated with the cardiac condition, monitor the discomfort parameter during execution of the at least one pacing routine, determine whether the discomfort parameter transgresses the at least one of the range of values and the patient discomfort threshold value, and adjust at least one characteristic of the at least one pacing routine upon the discomfort parameter transgressing the at least one of the range of values and the patient discomfort threshold value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation-in-Part of U.S. patent applicationSer. No. 15/079,294, titled “MEDICAL MONITORING AND TREATMENT DEVICEWITH EXTERNAL PACING,” filed on Mar. 24, 2016, which is a Continuationof U.S. patent application Ser. No. 14/610,600, titled “MEDICALMONITORING AND TREATMENT DEVICE WITH EXTERNAL PACING,” filed on Jan. 30,2015, now U.S. Pat. No. 8,983,597, which is a Continuation of U.S.patent application Ser. No. 13/907,523, titled “MEDICAL MONITORING ANDTREATMENT DEVICE WITH EXTERNAL PACING,” filed on May 31, 2013, now U.S.Pat. No. 8,983,597, which claims priority under 35 U.S.C. § 119(e) toU.S. Provisional Application Ser. No. 61/653,889, titled “NONINVASIVEAMBULATORY MONITORING AND TREATMENT DEVICE WITH EXTERNAL PACING,” filedon May 31, 2012, each of which is hereby incorporated herein byreference in its entirety. This Application also claims the benefit ofU.S. Provisional Patent Application Ser. No. 62/185,940, titled“EXTERNAL PACING DEVICE WITH DISCOMFORT MANAGEMENT,” filed on Jun. 29,2015, which is hereby incorporated by reference in its entirety.

BACKGROUND

Technical Field

The present disclosure is directed to noninvasive ambulatory medicaldevices, and more particularly, to a non-invasive medical monitoring andtreatment device that is capable of externally pacing the heart of apatient wearing the device.

Discussion

Cardiac arrest and other cardiac health ailments are a major cause ofdeath worldwide. Various resuscitation efforts aim to maintain thebody's circulatory and respiratory systems during cardiac arrest in anattempt to save the life of the victim. The sooner these resuscitationefforts begin, the better the victim's chances of survival.

To protect against cardiac arrest and other cardiac health ailments,some at-risk patients may use a wearable defibrillator, such as theLifeVest® wearable cardioverter defibrillator available from ZOLL®Medical Corporation of Chelmsford, Mass. To remain protected, thepatient wears the device continuously or nearly continuously while goingabout their normal daily activities, while awake, and while asleep.

SUMMARY

Some aspects and embodiments of the present disclosure relate tocontrolling patient discomfort during administration of external pacingto the heart. For example, the systems and techniques described hereincan be used in various medical monitoring and/or treatment devices. Insome examples, the medical devices can be external or non-invasive,e.g., in contrast to internal or invasive devices, such as implantablemedical devices. In some examples, a medical device as described hereincan be bodily-attached, e.g., at least a portion of the device (otherthan its electrodes in the case of a defibrillator, cardioverter orpacer) is removably attached to the body of a patient, such as bymechanical coupling (for example, by a wrist strap, cervical collar,bicep ring), adhesion (for example, by an adhesive gel intermediary),suction, magnetism, fabric or other flexible material (for example, bystraps or integration into a garment) or other body mounting featuresnot limited by the aforementioned examples. In some examples, suchcoupling elements can hold the device in a substantially fixed positionwith respect to the body of the patient. In some examples, a medicaldevice as described herein can be ambulatory, e.g., the device iscapable of and designed for moving with the patient as the patient goesabout his or her daily routine.

One example of a medical monitoring and treatment device suited for usewith the systems and techniques described herein is the LifeVest®Wearable Cardioverter Defibrillator available from ZOLL® MedicalCorporation of Chelmsford, Mass. A medical monitoring and treatmentdevice can provide lifesaving defibrillation treatment to a patientsuffering a treatable form of cardiac arrhythmia such as ventricularfibrillation (VF) or ventricular tachycardia (VT). Applicants haveappreciated that such a medical monitoring and treatment device can beconfigured to perform a variety of different types of cardiac pacing totreat a wide variety of different cardiac arrhythmias, such asbradycardia, tachycardia, an irregular cardiac rhythm, and asystole(including asystole after a therapeutic shock). Applicants have furtherappreciated that, in other embodiments, a medical monitoring andtreatment device can be configured to perform pacing to treat pulselesselectrical activity. In accordance with an aspect of the presentdisclosure, the medical monitoring and treatment device can beconfigured to pace the heart of the patient at a fixed energy level(e.g., fixed current, fixed voltage, etc.) and pulse rate, to pace theheart of the patient on demand with a fixed energy level and anadjustable rate responsive to the detected intrinsic activity level ofthe patient's heart, or to pace the heart of the patient using capturemanagement with an adjustable energy level and adjustable rateresponsive to the detected intrinsic rate of the patient's heart and thedetected response of the patient's heart to pacing, including both on abeat-by-beat basis and as analyzed over other various time intervals.

In some examples, the pacing parameters described above may be adjustedto lessen any discomfort experienced by the patient during pacing. Invarious examples, the patient can self-manage the administration of thepacing routine based on his or her own tolerance of the discomfort. Inthese examples, the medical monitoring and treatment device may beginpacing a patient using either default pacing parameters or baselinepacing parameters tailored to discomfort tolerances of the patient. Thebaseline pacing parameters may be configured by executing the medicalmonitoring and treatment device in a baseline mode during an initial fitof the device to the patient or by executing (or re-executing) themedical monitoring and treatment device in a baseline mode duringsubsequent operation of the device. It is appreciated that the pacingparameters may control, for example, the administration of pacingpulses, various characteristics of the pacing pulses, the administrationof TENS pulses, and/or various characteristics of the TENS pulses.

In one aspect of the present invention, an external medical device isprovided comprising at least one therapy electrode configured to bedisposed on a patient, and a treatment manager, coupled to the at leastone therapy electrode, configured to execute a baseline process todetermine at least one of a range of values for a discomfort parametercorresponding to at least one pacing routine and a patient discomfortthreshold value corresponding to the at least one pacing routine, detecta cardiac condition of the patient, execute the at least one pacingroutine, the at least one pacing routine being associated with thecardiac condition, monitor the discomfort parameter associated with thepatient during execution of the at least one pacing routine, determinewhether the discomfort parameter transgresses the at least one of therange of values and the patient discomfort threshold value, and adjustat least one characteristic of the at least one pacing routine inresponse to determining that the discomfort parameter transgresses theat least one of the range of values and the patient discomfort thresholdvalue. In one embodiment, the device further comprises a user interfacefor receiving discomfort information regarding the patient in connectionwith the at least one pacing routine. In one embodiment, the discomfortparameter is based on at least one of the discomfort informationreceived from a user via the user interface and informationautomatically detected by at least one sensor distinct from the userinterface. In another embodiment, the user interface comprises at leastone of a touch screen, a button, a microphone for receiving audiblecommands, a strain gauge, a force sensor, a piezoelectric transducer,and a rotating spring-loaded dial.

In an alternative embodiment, the treatment manager is configured toreceive the discomfort information descriptive of the discomfortparameter with reference to an amount of pressure exerted by the user onan element of the user interface. In one embodiment, the treatmentmanager is configured to determine a present value of the discomfortparameter during execution of the at least one pacing routine based onat least one of an amount of pressure detected by the user interface anda duration of time the element of the user interface remains actuated.In one embodiment, the element of the user interface is at least one ofa quartz sensor, a ceramic force sensor, and a piezoelectric transducer.In another embodiment, the user interface comprises a force sensorconfigured to detect a force applied by the user squeezing at least onesurface of the force sensor. In yet another embodiment, the at least onesensor includes at least one of a motion sensor, an audio sensor, aphysiological sensor, an electrode, an accelerometer, and a bloodpressure sensor.

In one embodiment, the treatment manager is configured to receive thediscomfort information regarding the patient responsive to selection ofan element of the user interface. In one embodiment, the user interfacedisplays a discomfort scale and the element includes a selectable pointon the discomfort scale. In one embodiment, the discomfort scale is atleast one of numeric and image-based. In one embodiment, the userinterface includes a touch screen configured to display a plurality ofselectable points on the discomfort scale. In another embodiment, theselection includes at least one of a touch and an utterance. In analternative embodiment, the utterance includes at least one predefinedword.

In another embodiment, the treatment manager is further configured todetect, via a touch detector, a touch having a duration, and determinewhether the discomfort parameter transgresses the patient discomfortthreshold value based on the duration. In one embodiment, the treatmentmanager is further configured to adjust at least one characteristic ofthe at least one pacing routine in response to determining that a valueof the discomfort parameter is equal to or transgresses the patientdiscomfort threshold value. In one embodiment, the at least onecharacteristic of the at least one pacing routine includes at least oneof an amplitude of pacing pulses, a width of the pacing pulses, a rateof the pacing pulses, a waveform of the pacing pulses, a period of thepacing pulses, a duty cycle of the pacing pulses, and a ramp timeconstant of the pacing pulses. In another embodiment, the cardiaccondition comprises at least one of bradycardia, tachycardia, asystole,pulseless electrical activity, and erratic heart rate.

In one embodiment, the at least one pacing routine comprises at leastone of fixed rate pacing, fixed energy pacing, adjustable rate pacing,and capture management pacing. In one embodiment, the discomfortparameter is indicative of a level of discomfort experienced by thepatient during the at least one pacing routine. In one embodiment, thetreatment manager is configured to execute the baseline process duringan initial fitting of the external medical device to the patient. Inanother embodiment, the treatment manager is further configured tooptimize at least one characteristic of the at least one pacing routinein response to the determination that the discomfort parametertransgresses the at least one of the range of values and the patientdiscomfort value.

In an alternative embodiment, the treatment manager is configured tooptimize the at least one characteristic along a scale selected from atleast one of a linear scale, a logarithmic scale, and an exponentialscale. In one embodiment, the treatment manager is configured tooptimize the at least one characteristic at least in part by executing aregression analysis using historical values of the at least onecharacteristic. In one embodiment, the treatment manager is furtherconfigured to adjust the patient discomfort threshold value based on thepatient's state of consciousness. In another embodiment, the devicefurther comprises a transcutaneous electrical nerve stimulation unitconfigured to provide background stimulation to the patient duringexecution of the at least one pacing routine.

In one embodiment, executing the baseline process further comprisessetting at least one characteristic of the at least one pacing routineto an appropriate level based on a physiological condition of thepatient. In one embodiment, the appropriate level is determined based ontypical impedance values for an adult or child. In another embodiment,executing the baseline process further comprises setting at least onecharacteristic of the at least one pacing routine with reference topacing parameter baselines associated with multiple patients.

In another aspect of the present invention, a method of controllingpatient discomfort during pacing by an external medical device isprovided comprising determining, during a baseline process, at least oneof a range of values for a discomfort parameter corresponding to atleast one pacing routine of the external medical device and a patientdiscomfort threshold value corresponding to the at least one pacingroutine, detecting a cardiac condition of the patient, the cardiaccondition being associated with the at least one pacing routine,executing the at least one pacing routine, monitoring the discomfortparameter of the patient during execution of the at least one pacingroutine, and adjusting, responsive to the discomfort parametertransgressing at least one of the range of values and the patientdiscomfort threshold value, at least one characteristic of the at leastone pacing routine. In one embodiment, the method further comprisesreceiving, via a user interface, discomfort information regarding thepatient in connection with the at least one pacing routine. In oneembodiment, the discomfort parameter is based on at least one of thediscomfort information received from a user via the user interface andinformation automatically detected by at least one sensor distinct fromthe user interface. In another embodiment, the method further comprisesreceiving the discomfort information from a user selection of an elementof the user interface.

In one embodiment, the user interface comprises a touch sensor, themethod further comprising detecting, via the touch sensor, a touchhaving a duration, and determining whether the discomfort parameter isequal to or transgresses the patient discomfort threshold value withreference to the duration. In another embodiment, executing the baselineprocess further comprises setting at least one characteristic of the atleast one pacing routine to an appropriate level based on at least oneof a physiological condition of the patient, typical impedance valuesfor an adult or child, and pacing parameter baselines associated withmultiple patients.

In an alternative aspect of the present invention, a bodily-attachedambulatory medical device is provided comprising at least one therapyelectrode configured to be disposed on a patient, and a treatmentmanager, coupled to the at least one therapy electrode, configured toexecute a baseline process to determine at least one of a range ofvalues for a discomfort parameter corresponding to at least one pacingroutine and a patient discomfort threshold value corresponding to the atleast one pacing routine, detect a cardiac condition of the patient, andexecute the at least one pacing routine, the at least one pacing routinebeing associated with the cardiac condition and having at least onecharacteristic configured for the patient's tolerance for discomfortbased on the at least one of the range of values for the discomfortparameter and the patient discomfort threshold value.

Still other aspects, embodiments, and advantages of these exemplaryaspects and embodiments are discussed in detail below. Moreover, it isto be understood that both the foregoing information and the followingdetailed description are merely illustrative examples of various aspectsand embodiments of the present disclosure, and are intended to providean overview or framework for understanding the nature and character ofthe claimed aspects and embodiments. Any embodiment or example disclosedherein may be combined with any other embodiment or example in anymanner consistent with at least one of the aspects disclosed herein, andreferences to “an embodiment,” “an example,” “some embodiments,” “someexamples,” “an alternate embodiment,” “an alternate example,” “variousembodiments,” “various examples,” “one embodiment,” “one example,” “atleast one embodiment,” “at least one example,” “this and otherembodiments,” “this and other examples,” or the like are not necessarilymutually exclusive and are intended to indicate that a particularfeature, structure, or characteristic described in connection with theembodiment may be included in at least one embodiment. The appearance ofsuch terms herein is not necessarily all referring to the sameembodiment.

Furthermore, in the event of inconsistent usages of terms between thisdocument and documents incorporated herein by reference, the term usagein the incorporated references is supplementary to that of thisdocument; for irreconcilable inconsistencies, the term usage in thisdocument controls. In addition, the accompanying drawings are includedto provide illustration and a further understanding of the variousaspects and examples, and are incorporated in and constitute a part ofthis specification. The drawings, together with the remainder of thespecification, serve to explain principles and operations of thedescribed and claimed aspects and examples.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In thedrawings, components that are identical or nearly identical may berepresented by a like numeral. For purposes of clarity, not everycomponent is labeled in every drawing. In the drawings:

FIG. 1 is an illustration of one example of a wearable medical device;

FIGS. 2A-2B are illustrations of one example of a medical devicecontroller for an ambulatory medical device;

FIG. 3 is a functional schematic of one example of a medical devicecontroller;

FIG. 4 is a flow diagram of one example baseline generation process;

FIG. 5 is a flow diagram of one example pacing management process;

FIG. 6 is a flow diagram of one example managed pacing routine;

FIG. 7 is a flow diagram of one example managed pacing routine;

FIG. 8 is a flow diagram of one example managed pacing routine;

FIG. 9 is a graph illustrating various aspects of demand pacing whichcan be adjusted in connection with on demand pacing or capturemanagement pacing;

FIG. 10 is a graph illustrating a pacing waveform that may be providedby the medical monitoring and treatment device;

FIG. 11 is a graph illustrating another pacing waveform that may beprovided by the medical monitoring and treatment device;

FIG. 12 is a graph illustrating another pacing waveform that may beprovided by the medical monitoring and treatment device;

FIG. 13 is a graph illustrating another pacing waveform that may beprovided by the medical monitoring and treatment device;

FIG. 14 is a graph illustrating another pacing waveform that may beprovided by the medical monitoring and treatment device;

FIG. 15 is a graph illustrating a number of different pacing waveformsthat may be provided by the medical monitoring and treatment device,including a 40 ms constant current pulse;

FIG. 16 is a flow diagram of one example managed pacing routine; and

FIG. 17 is a flow diagram of one example baseline generation process.

DETAILED DESCRIPTION

Medical monitoring and treatment devices in accord with various examplesdisclosed herein are configured to monitor and control discomfortexperienced by a patient while administering therapy to the patient. Forinstance, in at least one example, a medical device is configured toprovide pacing therapy to a patient and to control parameters of apacing routine to decrease the level of discomfort experienced by thepatient. In some examples, the medical device is configured to allow thepatient to self-manage execution of the pacing routine (e.g.,dynamically control one or more parameters of the pacing routine) basedon his or her own tolerance of the discomfort in real time or near realtime.

In some examples, the medical device is configured to receive inputdescriptive of a level of discomfort being experienced by the patient,calculate a value quantifying of the level of discomfort beingexperienced by the patient, determine whether the value is equal to ortransgresses a discomfort threshold value, and, if so, adjust aparameter of the pacing routine to decrease the level of discomfort.

Medical devices disclosed herein may be invasive or non-invasive. Forexample, medical devices disclosed herein may be monitoring devices(e.g., configured to monitor a cardiac signal of a patient) with orwithout an associated treatment component. For example, a non-invasivemedical device suited for use with the systems and techniques asdisclosed herein can include an automated external defibrillator (AED).Such AEDs are capable of monitoring cardiac rhythms, determining when adefibrillating shock is needed, and administering the shock eitherautomatically or under the control of a trained rescuer (e.g., an EMT orother medically trained personnel). The AED may also be configured toprovide cardiopulmonary resuscitation (CPR) counseling. Such AEDs areavailable from ZOLL® Medical Corporation of Chelmsford, Mass.

The devices as described herein may be capable of continuously,substantially continuously, long-term and/or extended use or wear by, orattachment or connection to a patient.

For example, devices as described herein may be capable of being used orworn by, or attached or connected to a patient, without substantialinterruption for a predetermined period of time. In some examples, suchdevices may be capable of being used or worn by, or attached orconnected to a patient for example, up to hours or beyond (e.g., weeks,months, or even years).

In some implementations, such devices may be removed for a period oftime before use, wear, attachment, or connection to the patient isresumed, e.g., to change batteries, to change the garment, and/or totake a shower, without departing from the scope of the examplesdescribed herein.

The devices as described herein may be capable of continuously,substantially continuously, long-term and/or extended monitoring of apatient.

For example, devices as described herein may be capable of providingcardiac monitoring without substantial interruption for a predeterminedperiod of time. In some examples, such devices may be capable ofcontinuously or substantially continuously monitoring a patient forcardiac-related information (e.g., ECG information, including arrhythmiainformation, heart sounds, etc.) and/or non-cardiac information (e.g.,blood oxygen, the patient's temperature, glucose levels, and/or lungsounds), for example, up to hours or beyond (e.g., weeks, months, oreven years).

In some implementations, such devices may be powered down for a periodof time before monitoring is resumed, e.g., to change batteries, tochange the garment, and/or to take a shower, without departing from thescope of the examples described herein.

In some instances, the devices may carry out its monitoring in periodicor aperiodic time intervals or times. For example, the monitoring duringintervals or times can be triggered by a user action or another event.For example, one or more durations between the periodic or aperiodicintervals or times can be user-configurable.

In various implementations, the devices may be operated on battery powerfor a duration of the device's use after which the batteries may bereplaced and/or recharged.

The examples of the methods and apparatuses discussed herein are notlimited in application to the details of construction and thearrangement of components set forth in the following description orillustrated in the accompanying drawings. The methods and apparatusesare capable of implementation in other examples and of being practicedor of being carried out in various ways. Examples of specificimplementations are provided herein for illustrative purposes only andare not intended to be limiting. In particular, acts, elements andfeatures discussed in connection with any one or more examples are notintended to be excluded from a similar role in any other examples.

In implementations where example numerical values are provided (e.g., asa predetermined numerical value), it should be understood that suchvalues can be set through one or more user-configurable parameters. Forexample, the example numerical value can be provided as a default value,and a technician or a caregiver (such as a nurse or physician) canmodify the values in accordance with the principles described hereinthrough a user interface.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. Any references toexamples or elements or acts of the systems and methods herein referredto in the singular may also embrace examples including a plurality ofthese elements, and any references in plural to any example or elementor act herein may also embrace examples including only a single element.References in the singular or plural form are not intended to limit thepresently disclosed systems or methods, their components, acts, orelements.

The use herein of “including,” “comprising,” “having,” “containing,”“involving,” and variations thereof is meant to encompass the itemslisted thereafter and equivalents thereof as well as additional items.References to “or” may be construed as inclusive so that any termsdescribed using “or” may indicate any of a single, more than one, andall of the described terms.

Example Wearable Medical Device

In one example, the medical monitoring and treatment device is awearable medical device that includes a garment (e.g., a vest or belt)that is worn by the patient. The wearable medical device monitors thepatient's electrocardiogram (ECG) with sensing electrodes, detectslife-threatening arrhythmias, and delivers pacing pulses or acardioverting or defibrillating shock through therapy pads if treatmentis necessary. In examples, the wearable medical device is configured tomonitor the patient and the patient's environment to quantify a level ofdiscomfort being experienced by the patient and optimize theeffectiveness of a pacing routine while preventing the level ofdiscomfort of the patient from exceeding a threshold.

FIG. 1 illustrates an example wearable medical device for use with thesystems and techniques described herein. As shown, the wearable medicaldevice 100 includes a harness 110 having a pair of shoulder straps and abelt that is worn about the torso of a patient. The harness 110 istypically made from a material, such as cotton, nylon, spandex, orantron® that is breathable, and unlikely to cause skin irritation, evenwhen worn for prolonged periods of time. The wearable medical device 100includes a plurality of ECG sensing electrodes 112 that are attached tothe harness 110 at various positions about the patient's body andelectrically coupled (wirelessly or by a wired connection) to a sensorinterface of the medical device controller 120 via a connection pod 130.The plurality of ECG sensing electrodes 112, which may be dry-sensingcapacitance electrodes, are coupled to the medical device controller 120to monitor the cardiac function of the patient and generally include afront-back (FB) pair of ECG sensing electrodes and a side-side (SS) pairof ECG sensing electrodes. Additional ECG sensing electrodes may beprovided, and the plurality of ECG sensing electrodes 112 may bedisposed at varying locations about the patient's body. The plurality ofECG sensing electrodes 112 may incorporate any electrode system,including conventional stick-on adhesive electrodes, dry-sensingcapacitive ECG electrodes, radio transparent electrodes, segmentedelectrodes, or one or more long term wear electrodes that are configuredto be continuously or substantially continuously worn by a patient forextended periods (e.g., 3 or more days). One example of such a long termwear electrode is described in U.S. Patent Application Publication No.US2013/0325096 (hereinafter the “'096 publication”), titled “LONG TERMWEAR MULTIFUNCTION BIOMEDICAL ELECTRODE,” published Dec. 5, 2013, whichis hereby incorporated herein by reference in its entirety.

The wearable medical device disclosed herein may incorporate sundrymaterials arranged in a variety of configurations to maintain a properfit with the patient's body. For example, some embodiments include agarment as described in U.S. Patent Application Publication No.US2012/0283794, titled “PATIENT-WORN ENERGY DELIVERY APPARATUS ANDTECHNIQUES FOR SIZING SAME,” published Nov. 8, 2012, which is herebyincorporated herein by reference in its entirety. In one example, thegarment includes one or more strain gauges configured to generatesignals when pressed upon by the patient or when the patient twists awayfrom a source of discomfort. In this example, the amount of deformationindicated by the signals is quantified by the wearable medical devicefor use in managing the discomforted experience by the patient. Thusembodiments are not limited to the configuration and materials describedabove with reference to FIG. 1.

The wearable medical device 100 also includes a plurality of therapyelectrodes 114 a and 114 b that are electrically coupled to the medicaldevice controller 120 via the connection pod 130 and which areconfigured to deliver one or more therapeutic pacing pulses ordefibrillating shocks to the body of the patient, if it is determinedthat such treatment is warranted. As shown, the therapy electrodes 114include a first therapy electrode 114 a that is disposed on the front ofthe patient's torso and a second therapy electrode 114 b that isdisposed on the back of the patient's torso. The second therapyelectrode 114 b includes a pair of therapy electrodes that areelectrically coupled together and act as the second therapy electrode114 b. The use of two therapy electrodes 114 a, 114 b permits a pacingpulse or other therapeutic shock having any of a variety of waveforms tobe delivered to the body of the patient. The plurality of therapyelectrodes 114 may incorporate any electrode system, includingconventional stick-on adhesive electrodes, segmented electrodes,integrated electrodes (e.g., including electrode patches or assembliesintegrating both sensing and therapy electrodes), or one or more longterm wear electrodes that are configured to be continuously orsubstantially continuously worn by a patient for extended periods (e.g.,3 or more days). Example electrodes are described in '096 publication,which is hereby incorporated herein by reference in its entirety.

One of these waveforms is a biphasic waveform in which a first of thetwo therapy electrodes can deliver a first phase of the biphasic pulseor shock with the other therapy electrode acting as a return, and theother therapy electrode can deliver the second phase of the biphasicpulse or shock with the first therapy electrode acting as the return.Other waveforms may be generated by this arrangement and several aredescribed further below.

In some examples, the wearable medical device includes one or morereservoirs of conductive gel. In these examples, the wearable medicaldevice is configured to, prior to delivering the pulses or shock, deploythe conductive gel from the reservoir to reduce an impedance encounteredby the therapy electrodes during the delivery of the pacing pulses or adefibrillating shock.

The connection pod 130 electrically couples the plurality of ECG sensingelectrodes 112 and the plurality of therapy electrodes 114 to themedical device controller 120, and may include electronic circuitry. Forexample, in one implementation the connection pod 130 includes signalacquisition circuitry, such as a plurality of differential amplifiers toreceive ECG signals from different electrodes of the plurality of ECGsensing electrodes 112 and to provide a differential ECG signal to themedical device controller 120 based on the difference there between. Theconnection pod 130 may also include other electronic circuitry, such asa motion sensor or accelerometer through which patient activity may bemonitored.

In some embodiments, both the first therapy electrode 114 a and thesecond therapy electrode 114 b are disposed on the front of thepatient's torso. For example, the first therapy electrode 114 a may belocated external to the apex of the heart and the second therapyelectrode 114 b may be located along the parasternal line. Thusembodiments are not limited to a particular arrangement of therapyelectrodes.

In some embodiments, the plurality of ECG sensing electrodes 112 arepositioned and paired such that artifacts generated from electricalactivity are decreased. In other embodiments, the electronic circuitryincluded in the medical device controller 120 may equalize artifactsmeasured at electrodes by changing a gain or impedance. Other techniquesof decreasing or preventing artifacts within measured electricalactivity that may be used in conjunction with the embodiments disclosedherein are explained in U.S. Pat. No. 8,185,199, titled “MONITORINGPHYSIOLOGICAL SIGNALS DURING EXTERNAL ELECTRICAL STIMULATION,” issuedMay 22, 2012, which is hereby incorporated herein by reference in itsentirety.

Although not shown, the wearable medical device 100 may includeadditional sensors, other than the ECG sensing electrodes 112, capableof monitoring the physiological condition or activity of the patient.For example, sensors capable of measuring blood pressure, muscularcontraction, perspiration, heart rate, heart sounds, thoracic impedance,pulse oxygen level, respiration rate, and the activity level of thepatient may also be provided.

As shown in FIG. 1, the wearable medical device 100 may include a userinterface pod 140 that is electrically coupled to, integrated in, and/orintegrated with, the user interface of the medical device controller120. The user interface pod 140 can be attached to the patient'sclothing or to the harness 110, for example, via a clip (not shown) thatis attached to a portion of the interface pod 140. Alternatively, theuser interface pod 140 may simply be held in a person's hand. Forexample, such a user interface pod 140 can be a smartwatch or asmartphone. In some examples, the user interface pod 140 may communicatewirelessly with the user interface of the medical device controller 120,for example, using a Bluetooth®, Wireless USB, ZigBee, WirelessEthernet, GSM, or other type of communication interface.

The user interface pod 140 includes a number of buttons by which thepatient, or a bystander can communicate with the medical devicecontroller 120, and a speaker by which the medical device controller 120may communicate with the patient or the bystander. For example, wherethe medical device controller 120 determines that the patient isexperiencing cardiac arrhythmia, the medical device controller 120 mayissue an audible alarm via a speaker on the medical device controller120 or the user interface pod 140 alerting the patient and anybystanders to the patient's medical condition. Examples of notificationsissued by the medical device controller 120 are described in U.S. PatentApplication Publication No. US2012/0293323, titled “SYSTEM AND METHODFOR ADAPTING ALARMS IN A WEARABLE MEDICAL DEVICE,” published Nov. 22,2012, which is hereby incorporated herein by reference in its entirety.

In some examples, the medical device controller 120 may instruct thepatient to press and hold one or more buttons on the user interface ofthe medical device controller 120 or on the user interface pod 140 toindicate that the patient is conscious, thereby signaling the medicaldevice controller 120 to withhold the delivery of one or moretherapeutic pacing pulses or defibrillating shocks. If the patient doesnot respond, the device may determine that the patient is unconscious,and proceed with the treatment sequence, culminating in delivery ofdefibrillating shocks or one or more pacing pulses with parameters setto maximum values to the body of the patient.

In some examples, as described in detail below, the medical devicecontroller 120 may (depending on a type of user interface element, e.g.,one or more buttons on a user interface) instruct the patient to pressand hold the one or more buttons on the user interface with a forceproportional to the intensity of discomfort being experienced by thepatient during execution of a pacing routine, thereby signaling themedical device controller 120 to adjust parameters of the pacing routineto decrease the intensity of the discomfort. If the patient does notrespond, the device may determine that the patient is unconscious, andproceed with the treatment sequence, culminating in the delivery of oneor more pacing pulses to the body of the patient. For example, themedical device may administer a pacing routine with values for thepacing parameters as an upper bound of a range of values (e.g., tomaximize efficacy) as described below. As the patient recoversconsciousness, the patient may (depending on a type of user interfaceelement), in real time or near real time, increase the force exerted onthe one or more buttons, thereby signaling the medical device to adjustthe parameters of the pacing routine. The medical device may, inresponse to receiving the signal, decrease the intensity of thediscomfort by, for example, decreasing the values of the pacingparameters (which may result in a corresponding decrease in efficacy).If the patient were to once again lose consciousness or feel faint,e.g., as a result of bradycardia, the patient may not be able tocontinue to exert a same level of force on the one or more buttons.Correspondingly, the medical device can dynamically adjust the values ofthe pacing parameters to increase the efficacy of the pacing routine.

In some situations where the patient fails to provide voluntary feedbackregarding his/her level of discomfort, a threshold value can be set fora discomfort parameter as outlined below. When the sensed level ofdiscomfort is equal to or transgresses the threshold, the medical devicecan adjust the values of the pacing parameters to lower the intensity ofthe pacing routine. In some examples, the medical device can check forcapture before, after, or substantially simultaneous with adjusting thevalues of the pacing parameters as described in further detail below.

In some implementations, one or more response buttons and/or userinterface elements for managing discomfort during a pacing routine maybe different from one or more response buttons for establishing userresponsiveness prior to delivering a defibrillating shock.

In another example, the functionality of the user interface pod 140 isintegrated into the housing of the medical device controller 120. FIGS.2A-2B illustrate such an example of the medical device controller 120.The medical device controller 120 includes two response buttons 210 onopposing sides of a housing 206 of the medical device controller 120. Asshown in FIGS. 2A-2B, the response buttons 210 are recessed to reducethe likelihood of accidental activation (e.g., a patient falling on theresponse button). The medical device controller 120 also includes, inthis example, a display screen 220 and a speaker 204 to enable thecommunication of audible and visual stimuli to the patient. It isappreciated that the response buttons 210 do not have to be placed onopposing sides of the housing as illustrated in FIGS. 2A-2B. Theresponse buttons 210, for example, may be located adjacent to each otherin the housing the ambulatory medical device controller. The adjacentplacement of the response buttons may make it easier for individualswith smaller hands or less dexterity to engage the response buttons. Themedical device controller 120 may further include a connector 202 toremovably connect sensing electrodes (e.g., ECG sensing electrodes 112)and/or therapy electrodes (e.g., therapy electrodes 114 a and 114 b) tothe medical device controller 120.

Another example wearable medical device includes an ambulatory externaldefibrillator described in FIG. 1 of U.S. Pat. 8,904,214, titled “SYSTEMAND METHOD FOR CONSERVING POWER IN A MEDICAL DEVICE,” issued Dec. 2,2014 (hereinafter the “'214 patent”), which is hereby incorporatedherein by reference in its entirety. In at least one example, theambulatory defibrillator 100 illustrated in FIG. 1 of the '214 patentmay employ the medical device controller 120, as disclosed in thepresent application, as a substitute for the medical device controller200 described in the '214 patent. In such an example, the ECG Electrodesand Therapy Pads illustrated in FIG. 1 of the '214 patent may belogically and physically coupled to the medical device controller 120.While some of the examples disclosed herein are directed to wearablemedical devices, the systems and methods disclosed herein may be readilyapplied to other medical devices including, for example, an AutomatedExternal Defibrillator (AED).

In some implementations, the medical device as described herein can be ahospital-based wearable defibrillator and/or pacing device. For example,such a hospital-based device can include a defibrillator and/or pacingdevice configured for continuous or substantially continuous use, wear,connection, attachment, or monitoring to/of a patient in a hospitalenvironment. The hospital-based device can include a plurality oftherapy and sensing electrodes that are attached to the patient's skin.In some examples, the electrodes are disposable adhesive electrodes. Insome implementations, the electrodes are affixed to an electrodeassembly (a patch), which can then be adhesively attached to thepatient's skin. The electrodes can be attached to the patient's skin atparticular locations as prescribed by a trained professional.

In operation, the hospital-based device can include a monitor configuredto operate in a manner that is different from that of the monitor ofwearable defibrillator described above with respect to FIG. 1. Forexample, an interface, prompts, and communication performed by thehospital-based device can be configured for and/or directed to a userother than the patient, e.g., a caregiver such as a nurse or a patientservice representative. For example, a caregiver can program the deviceand/or set the device up for use by the patient. The interface, prompts,and communication can be directed to the patient in scenarios such aswhen a response is required to let the device know whether or not thepatient is conscious, which can be used in deciding when to shock thepatient, and when a patient is given an alert to call the caregiver.

Example Medical Device Controller

FIG. 3 illustrates a medical device controller 300 that is configured tomonitor the cardiac activity of a patient and/or provide pacing or othertherapy to the patient as needed. The medical device controller 300 may,for example, be configured for use in a wearable medical device (e.g.,medical device controller 120). The medical device controller 300 has avariety of potential applications and is well suited to devices thatnotify external entities of one or more events of interest (e.g.,cardiac events). Examples of medical devices to which the medical devicecontroller 300 is well suited include critical care medical devices,such as a wearable ambulatory external defibrillator, an AED, pacingdevices, or a mechanical chest compression device, such as theAutopulse® system from ZOLL® Medical Corporation of Chelmsford, Mass.

As shown in FIG. 3, the medical device controller 300 includes aprocessor 318, a sensor interface 312, a treatment manager 314, atherapy delivery interface 302, data storage 304, a communicationnetwork interface 306, a user interface 308, and a battery 310. The datastorage 304 includes patient data 316 and discomfort scale data 332. Thetreatment manager 314 includes a cardiac monitor 320, a discomfortmonitor 322, one or more pacing routines 324, and a transcutaneouselectrical nerve stimulation (TENS) routine 334. Both the sensorinterface 312 and the network interface 306 are illustrated using dashedlines to indicate they are optional components in at least someexamples. The sensor interface 312, as illustrated, is coupled toelectrodes including a front-back (FB) electrode pair 326 and aside-side (SS) electrode pair 328.

The therapy delivery interface 302, as illustrated, can be coupled toone or more therapy electrodes, e.g., therapy electrode pair 330. Thetherapy delivery interface 302 may be optionally coupled to one or moreTENS electrodes (e.g., TENS electrodes 336) and/or one or more pacingelectrodes (e.g., pacing electrodes 338). For example, TENS electrodes336 may include a TENS electrode pair, and pacing electrodes 338 mayinclude a pacing electrode pair. It is appreciated that the electrodeconfiguration and/or the number of electrodes may be changed to bestsuit the particular application. For example, the therapy deliveryinterface 302 may be coupled to the therapy electrode pair 330 andprovide any combination of defibrillation pulses, pacing pulses, andTENS pulses to the patient via the therapy electrode pair 330. In someimplementations, the therapy delivery interface 302 may be coupled toseparate pacing electrodes 338 for providing pacing pulses in additionto the therapy electrode pair 330 for providing defibrillation pulses.Accordingly, the TENS pulses may be provided to the patient via eitherthe pacing electrodes 338 and/or the therapy electrode pair 330 undercontrol of a treatment protocol as described herein. As such, thetherapy delivery interface 302 may be coupled to any combination of thetherapy electrode pair 330, the TENS electrodes 336, and pacingelectrodes 338 to provide treatment to the patient.

In some examples, the therapy delivery interface 302 is coupled to atleast the therapy electrode pair 330 and the pacing electrodes 338.Employing the therapy electrode pair 330 to provide defibrillationpulses and separate pacing electrodes 338 to provide pacing pulses maybe advantageous, for example, where different electrode configurationsenable different gels to be deployed for pacing and defibrillation. Forexample, the therapy electrode pair 330 may be configured to deploy agel with a low impedance and the pacing electrodes 338 may be configuredto deploy a gel with a higher impedance. In these examples, the therapydelivery interface 302 may delivery defibrillation pulses via thetherapy electrode pair 330 and deliver pacing and/or TENS pulses via thepacing electrodes 338 and/or another electrode pair (e.g., TENSelectrodes 336).

For example, the therapy electrodes (or, in some implementations, pacingelectrodes) may deploy a high impedance gel (e.g., 500 ohms) to decreaseexternal skin pain during pacing routines as described herein. Forexample, the therapy electrodes may also be configured to dispense a lowimpedance gel (e.g., 1 ohm) should defibrillation be required before orafter pacing.

In some examples, the battery 310 is a rechargeable battery thatprovides electrical power to other components within the medical device.The particular capacity and type of battery (e.g., lithium ion,nickel-cadmium, or nickel-metal hydride) employed may vary based on thedesired runtime between charges of the medical device and the powerconsumption of the components. For example, the battery 310 may beselected to provide a minimum runtime between charges of 44 hours. Inthis example, a suitable battery may include a 3 cell 4200 mAh lithiumion battery pack. It is appreciated that various mechanisms may beemployed to removably secure the battery 310 to the medical devicecontroller 300 including, for example, a latching mechanism.

According to the example illustrated in FIG. 3, the processor 318 iscoupled to the sensor interface 312, the therapy delivery interface 302,the data storage 304, the network interface 306, and the user interface308. The processor 318 performs a series of instructions that result inmanipulated data which are stored in and retrieved from the data storage304. According to a variety of examples, the processor 318 is acommercially available processor such as a processor manufactured byTexas Instruments, Intel, AMD, Sun, IBM, Motorola, Freescale, and ARMHoldings. However, the processor 318 may be any type of processor,multiprocessor or controller, whether commercially available orspecially manufactured. For instance, according to one example, theprocessor 318 may include a power conserving processor arrangement suchas described in the '214 patent. In another example, the processor 318is an Intel® PXA270.

In addition, in some examples, the processor 318 may be configured toexecute a conventional operating system. The operating system mayprovide platform services to application software, such as some examplesof the treatment manager 314 which are discussed further below. Theseplatform services may include inter-process and network communication,file system management and standard database manipulation. One or moreof many operating systems may be used, and examples are not limited toany particular operating system or operating system characteristic. Forinstance, operating systems can include a Windows based operatingsystem, OSX, or other operating systems. For instance, in some examples,the processor 318 may be configured to execute a real time operatingsystem (RTOS), such as RTLinux, or a non-real time operating system,such as BSD or GNU/Linux.

In some examples, the treatment manager 314 is configured to monitor thecardiac activity of the patient, identify cardiac events experienced bythe patient, treat identified cardiac events, and manage discomfortexperienced by patients during treatment. In these examples, the cardiacmonitor 320 is configured to process data descriptive of cardiacfunction to identify cardiac events. The one or more pacing routines 324are configured to apply one or more pacing pulses via the therapyelectrode pair 330 to the patient to treat arrhythmias, such asbradycardia. For example, the wearable medical device can be configuredto treat a patient experiencing bradycardia when the patient's heartrate is about 40 beats per minute or less.

In some examples, prior to and during the execution of one or morepacing routines, the discomfort monitor 322 can request that the userinterface 308 instruct the patient to press and hold one or more buttonson the user interface with a force proportional to the intensity ofdiscomfort being experienced by the patient during execution of the oneor more pacing routines. In this manner, the discomfort monitor 322 canadjust the parameters of the pacing routine to increase or decrease theintensity of the one or more pacing routines based on the patient'scomfort level and/or efficacy of the routines. For example, if thepatient does not respond, the discomfort monitor 322 may determine thatthe patient is unconscious, and proceed with the treatment sequence,culminating in the delivery of one or more pacing pulses to the body ofthe patient. For example, the medical device may administer a pacingroutine with values for the pacing parameters as an upper bound of arange of values (e.g., to maximize efficacy) as described below. As thepatient recovers consciousness, the patient may (depending on a type ofuser interface element), in real time or near real time, increase theforce exerted on the one or more buttons of the user interface 308,thereby signaling the medical device to adjust the parameters of thepacing routine. The discomfort monitor 322 may, in response to receivingthe signal, decrease the intensity of the discomfort by, for example,decreasing the values of the pacing parameters (with a correspondingdecrease in efficacy).

In some implementations, the discomfort monitor 322 is configured toreceive input descriptive of patient discomfort, quantify a level ofdiscomfort being experienced by the patient, compare the quantifiedlevel of discomfort to a discomfort threshold value, and adjustparameters of the active pacing routine to decrease the level ofdiscomfort being experienced by the patient. One of the parameteradjustments that may be executed by the discomfort monitor 322 isexecution of the TENS routine 334. The TENS routine 334 is configured toapply one or more TENS pulses to a patient via, for example, one or moreTENS electrodes 336. It is appreciated that the TENS pulses may beapplied by other electrodes including, for example, the therapyelectrode pair 330 and/or one or more pacing electrodes 338.

These TENS pulses may serve to distract the patient so that the level ofdiscomfort experienced by the patient is lessened. In some examples, theTENS pulses are applied in intervals between pacing pulses. Additionaldescription regarding the use of TENS pulses in conjunction withexternal pacing is provided in U.S. Pat. No. 5,205,284, titled “METHODAND APPARATUS FOR TRANSCUTANEOUS ELECTRICAL CARDIAC PACING WITHBACKGROUND STIMULATION” and issued on Apr. 27, 1993, which is herebyincorporated herein by reference in its entirety.

Processes executed by the treatment manager 314 and its constituentcomponents (i.e., the cardiac monitor 320, the pacing routines 324, thediscomfort monitor 332, and the TENS routine 334) are described ingreater detail below with reference to FIGS. 4-15. The treatment manager314 and its constituent components may be implemented using hardware ora combination of hardware and software. For instance, in one example,the treatment manager 314 and its constituent components are implementedas software components that are stored within the data storage 304 andexecuted by the processor 318. In this example, the instructionsincluded in the treatment manager 314 and its constituent componentsprogram the processor 318 to execute the processes described herein. Inother examples, the treatment manager 314 and its constituent componentsmay be application-specific integrated circuits (ASICs) that are coupledto the processor 318. Thus, examples of the treatment manager 314 andits constituent components are not limited to particular hardware orsoftware implementations.

In some examples, the components disclosed herein, such as the treatmentmanager 314 and its constituent components, may read parameters thataffect the functions performed by the components. These parameters maybe physically stored in any form of suitable memory including volatilememory, such as RAM, or nonvolatile memory, such as a flash memory ormagnetic hard drive. In addition, the parameters may be logically storedin a propriety data structure, such as a database or file defined by auser mode application, or in a commonly shared data structure, such asan application registry that is defined by an operating system. Inaddition, some examples provide for both system and user interfaces, asmay be implemented using the user interface 308, that allow externalentities to modify the parameters and thereby configure the behavior ofthe components.

The data storage 304 includes a computer readable and writeablenonvolatile data storage medium configured to store non-transitoryinstructions and data. In addition, the data storage 304 includesprocessor memory that stores data during operation of the processor 318.In some examples, the processor memory includes a relatively highperformance, volatile, random access memory such as dynamic randomaccess memory (DRAM), static memory (SRAM) or synchronous DRAM. However,the processor memory may include any device for storing data, such as anon-volatile memory, with sufficient throughput and storage capacity tosupport the functions described herein. According to several examples,the processor 318 causes data to be read from the nonvolatile datastorage medium into the processor memory prior to processing the data.In these examples, the processor 318 copies the data from the processormemory to the non-volatile storage medium after processing is complete.A variety of components may manage data movement between thenon-volatile storage medium and the processor memory and examples arenot limited to particular data management components. Further, examplesare not limited to a particular memory, memory system or data storagesystem.

The instructions stored on the data storage 304 may include executableprograms or other code that can be executed by the processor 318. Theinstructions may be persistently stored as encoded signals, and theinstructions may cause the processor 318 to perform the functionsdescribed herein. The data storage 304 also may include information thatis recorded, on or in, the medium, and this information may be processedby the processor 318 during execution of instructions. The medium may,for example, be optical disk, magnetic disk or flash memory, amongothers, and may be permanently affixed to, or removable from, themedical device controller 300.

In some examples, the patient data 316 includes pacing parameterbaselines associated with one or more patients, one or more pacingroutines, or a combination of one or more patient parameter baselinesand one or more pacing routines. The pacing parameter baselines may bestored as, for example, a series of tuples that include a parameter namethat identifies a pacing parameter and a parameter value that specifiesa baseline value of the identified pacing parameter to be used when apacing routine is initiated for a patient. In some examples, each of theseries of tuples may further include a patient name that identifies thepatient and a pacing routine name that identifies a particular pacingroutine to which the identified pacing parameter applies. The discomfortscale data 332 includes information representing one or more discomfortscales that may be used to quantify a level of discomfort beingexperienced by a patient. For example, the discomfort scale data 332 mayinclude data representative of the Wong-Baker FACES® Pain Rating Scale.

As illustrated in FIG. 3, the treatment manager 314, the patient data316, and the discomfort scale data 332 are separate components. However,in other examples, the treatment manager 314, the patient data 316, andthe discomfort scale data 332 may be combined into a single component orre-organized so that a portion of the patient data 316 or the discomfortscale data 332 is included in the treatment manager 314. Such variationsin these and the other components illustrated in FIG. 3 are intended tobe within the scope of the examples disclosed herein.

The patient data 316 and the discomfort scale data 332 may be stored inany logical construction capable of storing information on a computerreadable medium including, among other structures, flat files, indexedfiles, hierarchical databases, relational databases, or object orienteddatabases. These data structures may be specifically configured toconserve storage space or increase data exchange performance. Inaddition, various examples organize the patient data 316 and thediscomfort scale data 332 into particularized and, in some cases, uniquestructures to perform the functions disclosed herein. In these examples,the data structures are sized and arranged to store values forparticular types of data, such as integers, floating point numbers,character strings, arrays, linked lists, and the like.

As shown in FIG. 3, the medical device controller 300 includes severalsystem interface components 302, 306, and 312. Each of these systeminterface components is configured to exchange, i.e. send or receive,data with one or more specialized devices that may be located within thehousing of the medical device controller 300 or elsewhere. Thecomponents used by the interfaces 302, 306, and 312 may include hardwarecomponents, software components or a combination of both hardware andsoftware components. Within each interface, these components physicallyand logically couple the medical device controller 300 to thespecialized devices. This physical and logical coupling enables themedical device controller 300 to communicate with and, in someinstances, power or control the operation of the specialized devices.These specialized devices may include physiological sensors, therapydelivery devices, and computer networking devices.

For instance, in some examples, the therapy delivery interface 302includes waveform-shaping circuitry that receives pulse stream outputand modifies signal characteristics of the pulse stream, e.g., pulseshape, polarity, and amplitude, to generate pacing pulses havingconfigurable signal parameters. In these examples, the therapy deliveryinterface 302 delivers the pacing pulses to the therapy electrodes 330,which together externally deliver the pacing pulses to the patient fortranscutaneous pacing of the patient's heart. Examples of the waveformsthat may be delivered via the therapy delivery interface 302 areillustrated in FIGS. 10-15.

According to various examples, the hardware and software components ofthe interfaces 302, 306, and 312 implement a variety of coupling andcommunication techniques. In some examples, the interfaces 302, 306, and312 use leads, cables or other wired connectors as conduits to exchangedata between the medical device controller 300 and specialized devices.In other examples, the interfaces 302, 306, and 312 communicate withspecialized devices using wireless technologies such as radio frequencyor infrared technology. The software components included in theinterfaces 302, 306, and 312 enable the processor 318 to communicatewith specialized devices. These software components may include elementssuch as objects, executable code, and populated data structures.Together, these software components provide software interfaces throughwhich the processor 318 can exchange information with specializeddevices. Moreover, in at least some examples where one or morespecialized devices communicate using analog signals, the interfaces302, 306, and 312 further include components configured to convertanalog information into digital information, and vice versa, to enablethe processor 318 to communicate with specialized devices.

As discussed above, the system interface components 302, 306, and 312shown in the example of FIG. 3 support different types of specializeddevices. For instance, the components of the sensor interface 312 couplethe processor 318 to one or more physiological sensors such as a bodytemperature sensors, respiration monitors, perspiration sensors,muscular contraction sensors, and electrocardiogram (ECG) sensingelectrodes, one or more environmental sensors such as atmosphericthermometers, airflow sensors, video sensors, audio sensors,accelerometers, GPS locators, and hygrometers, or one or more motiondetection sensors such as altimeters, accelerometers, and gyroscopes. Inthese examples, the sensors may include sensors with varying samplingrates, including wireless sensors. The sensor interface 312, asillustrated, is coupled to four ECG sensing electrodes that form afront-back (FB) electrode pair 326 and a side-side (SS) electrode pair328. The sensor interface may include various circuitry to amplify theECG signal detected by the electrodes, condition the received ECGsignal, and/or digitize the ECG signals as described in U.S. Pat. No.8,600,486, titled “METHOD OF DETECTING SIGNAL CLIPPING IN A WEARABLEAMBULATORY MEDICAL DEVICE” and issued on Dec. 3, 2013 (hereinafter the“'486 Application”), which is hereby incorporated herein by reference inits entirety. It is appreciated that the particular number of ECGsensing electrodes coupled to the sensor interface 312 and/or thepairing of the ECG sensing electrodes may vary based on the specificimplementation.

In some examples, the components of the therapy delivery interface 302couple one or more therapy delivery devices, such as capacitors,defibrillator electrodes, pacing electrodes or mechanical chestcompression devices, to the processor 318. It is appreciated that thefunctionality of the therapy delivery interface 302 may be incorporatedinto the sensor interface 312 to form a single interface coupled to theprocessor 318. Additional description regarding certain features, suchas the waveform-shaping circuitry described above, that may be includedin various examples is provided in U.S. Pat. No. 5,431,688, titled“METHOD AND APPARATUS FOR TRANSCUTANEOUS CARDIAC PACING” and issued onJul. 11, 1995, which is hereby incorporated herein by reference in itsentirety.

In some examples, the components of the network interface 306 couple theprocessor 318 to a computer network via a networking device, such as abridge, router or hub. According to a variety of examples, the networkinterface 306 supports a variety of standards and protocols, examples ofwhich include USB (via, for example, a dongle to a computer), TCP/IP,Ethernet, Wireless Ethernet, Bluetooth, ZigBee, M-Bus, CAN-bus, IP,IPV6, UDP, DTN, HTTP, HTTPS, FTP, SNMP, CDMA, NMEA and GSM. It isappreciated that the network interface 306 of medical device controller300 may enable communication between other medical device controllerswithin a certain range.

To ensure data transfer is secure, in some examples, the medical devicecontroller 300 can transmit data via the network interface 306 using avariety of security measures including, for example, TLS, SSL or VPN. Inother examples, the network interface 306 includes both a physicalinterface configured for wireless communication and a physical interfaceconfigured for wired communication. According to various examples, thenetwork interface 306 enables communication between the medical devicecontroller 300 and a variety of personal electronic devices including,for example, computer enabled glasses, wristwatches, earpieces, andphones.

In one example, the network interface 306 is also capable oftransmitting and/or receiving information to assist in managingdiscomfort while treating a patient. This may be accomplished throughone or more antennas integrated with or coupled to the network interface306, and consequently coupled to the processor 318. For example, the oneor more antennas may receive information representative of the pacingparameter baselines associated with the patient. The wireless signalsreceived by the antennas may be analyzed by the processor 318 togenerate pacing parameter baselines for the patient. The networkinterface 306 may also transmit signals descriptive of one or moregenerated pacing parameter baselines to an external system. For example,the medical device may transmit signals descriptive of the pacingparameter baselines associated with a patient to a computer systemassociated with a health care provider of the patient. The computersystem associated with the health care provider may transmit signalsdescriptive of the pacing parameter baselines to one or more othermedical devices employed to provide treatment to the patient.

Thus, the various system interfaces incorporated in the medical devicecontroller 300 allow the device to interoperate with a wide variety ofdevices in various contexts. For instance, some examples of the medicaldevice controller 300 are configured to perform a process of sendingcritical events and data to a centralized server via the networkinterface 306. An illustration of a process in accord with theseexamples is disclosed in U.S. Pat. No. 6,681,003, titled “DATACOLLECTION AND SYSTEM MANAGEMENT FOR PATIENT-WORN MEDICAL DEVICES,” andissued on Jan. 20, 2004, which is hereby incorporated herein byreference in its entirety.

As illustrated in FIG. 3 by dashed lines, the sensor interface 312 isoptional and may not be included in every example. For instance, apacing device may employ the medical device controller 300 to deliverpacing pulses at a regular, set rhythm and receive data descriptive ofthe intensity of discomfort experienced by a patient via the userinterface 308. Similarly, a pacing device may include the medical devicecontroller 300 to provide alarm functionality but may not include anetwork interface 306 where, for example, the ambulatory defibrillatoris designed to rely on the user interface 308 to announce alarms.

The user interface 308 shown in FIG. 3 includes a combination ofhardware and software components that allow the medical devicecontroller 300 to communicate with an external entity, such as a patientor other user. These components may be configured to receive informationfrom actions such as physical movement, verbal intonation, or thoughtprocesses. In addition, the components of the user interface 308 canprovide information to external entities. Examples of the componentsthat may be employed within the user interface 308 include keyboards,strain gauges, pressure sensors, quartz and/or ceramic force sensors,piezoelectric transducers, rotating switches (spring loaded orotherwise), elastic deformable solids (e.g., a stress relief ball),mouse devices, buttons, microphones, electrodes, touch screens, printingdevices, display screens, and speakers. In some examples, the electrodesinclude an illuminating element, such as an LED. In other examples, theprinting devices include printers capable of rendering visual or tactile(Braille) output.

In some examples, the user interface 308 may be configured to provideinformation to external entities regarding a cardiac event experiencedby the patient. For example, the user interface 308 may provide an alarmindicting that the patient has experienced an arrhythmia and is beingpaced. In these examples, the user interface may also receive input fromthe patient regarding any discomfort being experienced during pacing.For example, the user interface 308 may issue an alarm requesting thepatient to interact with at least one element of the user interface 308(e.g., push a button) to acknowledge the alarm and adjust parameters ofthe therapy (e.g., pacing pulses).

In some examples, functions of the treatment manager 314 may be dividedbetween a baseline mode (e.g., a “learning mode”), where pacingparameter baselines are generated, and a management mode, where thepacing parameter baselines are used to administer treatment to thepatient. As illustrated in FIG. 3, the treatment manager 314 isconfigured to execute various processes associated with the baselinemode and the management mode. The treatment manager 314 may receiverequests to enter either the baseline mode or the management mode fromanother component (e.g., the user interface 308). In response toreceiving a request to enter the baseline mode, the treatment manager314 executes a baseline process, such as the baseline process 400described below with reference to FIG. 4. In response to receiving arequest to enter the management mode, the treatment manager 314 executesa management process, such as the management process 500 described belowwith reference to FIG. 5. It is appreciated that the particulararchitecture shown in FIG. 3 is for illustration only and otherarchitectures and/or modes may be employed by the treatment manager 314.

Example Baseline Generation Process

In some examples, a treatment manager (e.g., the treatment manager 314described above with reference to FIG. 3) is configured to generatebaseline parameters associated with a patient, with a pacing routine, ora combination of both. The baseline parameters are indicative of apatient's tolerance for discomfort while being treated by execution ofone or more pacing routines. The baseline process can yield informationrelating to a patient's discomfort threshold and further establishbaseline values for the pacing parameters. In particular, the baselineprocess can yield a range of values for a discomfort parameter for thepatient. As noted below, the baseline process can calculate a thresholdvalue for the discomfort parameter from the range of values and use thisthreshold during active pacing management. In addition, the baselineprocess can determine baseline values for the pacing parameters to useas a starting point in the pacing management process.

FIG. 4 illustrates an example baseline process 400 performed by, forexample, the treatment manager when the medical device is executing inbaseline mode. In some examples, the baseline mode of the medical deviceis activated to initiate execution of the baseline process 400. Thebaseline process 400 may be performed before active patient monitoringbegins via the management process 500 (described below with respect toFIG. 5). As discussed below, in some implementations, the baselineprocess 400 can be repeated periodically, e.g., once every two weeks, orwhen triggered by an external event (e.g., user-triggered event) or aninternal event (e.g., automated detection of a triggering condition).

Example triggering conditions can include, without limitation, one ormore of a change in patient profile information or data (e.g., through amanual or automated remote or local download process), device or userinitiated periodic or aperiodic self-tests, mechanical impact detection(e.g., when the device is subject to forces beyond a predeterminedthreshold), tampering of the device, assembly and/or disassembly eventsinvolving the device, excess temperature and/or moisture events, batterychange events, post-shock delivery (e.g., a period of time after a shockor pacing pulse has been delivered), an arrhythmia warning or alertevent (e.g., when the patient is conscious and able to respond bypushing the response buttons), actuation of the response buttons (e.g.,actuation of the buttons in a predetermined manner), changes in and/ortampering of the gel deployment mechanism, detected excessive cablingand/or device strains, error conditions thrown by software, and softwareupdates.

During execution of the baseline process 400, the patient's tolerancefor discomfort can be recorded and analyzed as described below. A userinterface (e.g., the user interface 308 described above with referenceto FIG. 3) can provide messages and interact with a user (either thepatient or a caregiver) to allow the recording of the baseline pacingparameters. In some examples, the medical device notifies the user, viathe user interface, upon completion of the baseline process 400. Thepatient (or caregiver) can abort the baseline process 400 at any time.

In one example, the baseline process 400 includes acts of fitting themedical device to a patient, delivering a pacing test pattern,calculating a level of discomfort experienced by the patient duringdelivery of the pacing test pattern, adjusting characteristics of thepacing test pattern, recording the test data, and optimizing pacingparameters. The baseline process 400 may also include transmitting thebaseline parameters to an external system (e.g., a computer system of ahealth care provider associated with the patient) for storage, review,and analysis.

In act 402, the medical device is fitted to the patient. In someexamples, the act 402 includes adjusting physical aspects of the medicaldevice (e.g., a garment or belt) to fit snugly and securely to thepatient's body. The act 402 may further include initiation of thebaseline mode in the medical device via the user interface.

In act 404, the treatment manager initiates delivery of a test patternto the patient that includes one or more pacing pulses delivered throughone or more therapy electrodes (e.g., the therapy electrode pair 330described above with reference to FIG. 3) and, optionally, one or moreTENS pulses through one or more TENS electrodes (e.g., the TENSelectrodes 336, the therapy electrode pair 330, and/or the pacingelectrodes 338 described above with reference to FIG. 3). The pacingpulses and the TENS pulses included in the test pattern may have variedcharacteristics. These characteristics may be controlled by one or morepacing parameters (including TENS parameters) that are set by, forexample, the treatment manager 314 discussed above with reference toFIG. 3. Example characteristics that may vary from pulse to pulseinclude pacing pulse amplitude, pacing pulse width, pacing pulse rate,pacing pulse waveform, pacing pulse period, pacing pulse duty cycle,pacing pulse ramp time constant, TENS pulse width, TENS pulse rate, TENSpulse amplitude, and TENS waveform. The pacing pulse amplitude may varywithin a range of values between approximately 15 milliamps and 140milliamps. The pacing pulse width may vary within a range of valuesbetween approximately 2 milliseconds and 40 milliseconds. The pacingpulse rate may vary within a range of values between approximately 20pacing pulses per minute and 80 pacing pulses per minute. The pacingpulse period may vary within a range of values between approximately 20microseconds and 500 microseconds. The pacing pulse duty cycle may varywithin a range of values between approximately 10 percent and 100percent. The pacing pulse ramp time constant may vary within a range ofvalues between approximately 40 microseconds and 100 microseconds. Thepacing pulse waveform may vary within a range of values including arectilinear waveform, a pulse train waveform, a truncated exponentialwaveform, a variable waveform, and a biphasic waveform. The TENS pulseamplitude may vary within a range of values between approximately 0milliamps and 200 milliamps. The TENS pulse width may vary within arange of values between approximately 0.001 milliseconds and 0.5milliseconds. The TENS pulse rate may vary within a range of valuesbetween approximately 0.5 pulse per minute and 500 pulses per minute.The TENS pulse waveform may be selected to be any one of a rectilinearwaveform, a pulse train waveform, and a biphasic waveform.

In various examples, different TENS stimulation modes may be used toameliorate patient sensation and discomfort during cardiac pacing. Forexample, an optimal mode of TENS stimulation may be tested and adjustedduring a baselining process of the medical device, e.g., a fittingperiod of a wearable defibrillator and/or pacing device. For example,one or more of the following TENS stimulation modes can be used in anyof the examples described herein.

1. Constant or Continuous Mode.

In this example mode, a medical device administering TENS can constantlyoutput a set pulse rate, pulse width and amplitude. The pulse rate candetermine which theory of TENS should be administered (e.g., Gate orEndorphin theory). For example, the Gate theory of TENS implicates ahigh pulse rate (e.g., 80-150 Hz). Under the Gate theory, asymmetricalbiphasic square wave pulses administered at high frequencies areunderstood to block a pain signal from an end of a nerve to the brain.For example, the Endorphin theory is implicated at lower pulse rates(e.g., 1-10 Hz). Under the Endorphin theory, a rubbing and/or pulsingsensation delivered through TENS can trigger a release of endorphins atthe area when the TENS is applied.

In some implementations, the pulse width and amplitude can be set inaccordance with the patient's comfort preferences (e.g., enough to feelthe pulsing sensation, and just under the threshold of a musclecontraction). In an example, the TENS parameters can be set such thatthe patient is able to feel the stimulation while not finding itpainful.

In some examples, the Constant Mode can be used to determine thebaseline settings for the patient. Over time, the patient can acclimateto the perceived sensation of the output. In some implementations, inthe Constant or Continuous Mode of operation, the patient may acclimatesooner because there is no modulation or change in the settings.

2. Pulse Rate Modulation Mode.

In this example mode based on varying a frequency of the pulses, thedevice can shift the frequency setting to, e.g., 50% of the set valueover, e.g., 5 seconds. For example, if the pulse rate (in Hz) is set at100 Hz, the device can be configured to shift the frequency downwards toabout 50 Hz and, in some cases, upwards to about 150 Hz over a durationof, e.g., 5 seconds.

For example, if the pulse rate is set at 5 Hz, then the frequency canshift from about 3-8 Hz over, e.g., 5 seconds using the Endorphintheory. Accordingly, the patient may not acclimate to the sensation asquickly as in the Constant Mode.

3. Pulse Width Modulation Mode:

In this example mode, the sensations felt by the patient due to the TENSoutput of the device can be varied using shifts in pulse width. Forexample, the device can change the pulse width setting while holding thepulse rate (Hz) setting constant and determining what theory of TENS isto be used. The changing pulse width can keep the patient fromacclimating to the TENS output over time. When the pulse width isincreased (e.g., to about 50% over a 5 second cycle), the sensationtypically feels stronger. As a result of this change, each individualpulse lasts longer. In an example, the pulse width setting can be set tobe as high as possible without generating a visible muscle contractionor discomfort. Conversely, the pulse width setting can be decreased byup to, e.g., 50% of an initial setting over a 5 second cycle to ease thesensation felt by the patient.

4. Pulse Rate & Pulse Width Modulation Mode.

In this example mode, the device can be configured such that as thepulse rate (Hz) increases, the pulse width (uS) can be decreased andvice versa. The pulse rate (Hz) setting can determine whether the Gateor Endorphin Theory is to be applied. The pulse width can be used todetermine how long each pulse is delivered, but both the pulse rate andpulse width can shift over time to prevent acclimation.

5. Cycled Burst Mode.

In this example mode, the pulse rate and pulse width settings can beconfigured to remain constant, but the amplitude can be dropped to be ator near zero for a first predetermined amount of time, e.g., 2.5seconds. After this period elapses, the amplitude can be restored to theoriginal amplitude setting for a second predetermined amount of time,e.g., another 2.5 seconds. This process can be repeated. In this manner,the device can create a “tapping” or “rubbing” sensation. For example,the pulse rate setting (Hz) can be in the 80-120 Hz range and be able tocause the release of endorphins.

6. Optimal Settings Mode: Increase of set Pulse Width 40%, decrease ofset Pulse Rate 45% and decrease of set Amplitude 10% over a 3 secondperiod. Values return to original settings over the next 3 seconds.

In this example mode, the device can be configured to modulate some orall of the waveform settings as described herein to achieve maximumpatient comfort. For example, when the pulse width shifts to highersettings (e.g., more aggressive sensation) the amplitude (or power levelof the waveform) can be configured to drop, e.g., 10% of the originalsetting, to allow for an increase in the pulse width setting to ensurepatient comfort. The pulse rate (e.g., characterized in Hz) can be usedto determine whether the Gate or Endorphin theory of TENS is to beapplied. In some examples, the frequency can be shifted e.g., up to 40%,to prevent patient acclimation.

In implementations, the device can be configured to intelligently shiftall of the waveform settings to adjust in a predetermined pattern formaximizing patient comfort. For example, there can be a 90% shift in thepulse rate setting to allow for both the Gate and Endorphin Theories tobe used within the same mode. For example, assuming that the initialpulse rate is set at 80 Hz, a 90% shift can allow for the pulse rate toswing from, e.g., 85 Hz (Gate Theory) to about, e.g., 10 Hz (EndorphinTheory). For example, one or more of the above modes (e.g., the OptimalSettings Mode) may be suited for patients with pain conditions relatingto both parasympathetic and sympathetic nerve groups.

In some examples, the test pattern delivered by the initial execution ofthe act 404 includes one or more pacing pulses and one or more TENSpulses with mild characteristics that reside within the lower portionsof each range of values described above. For instance, in at least oneexample, these one or more pacing pulses have characteristics set to thelower bound (minimum) within their respective ranges of values. In theseexamples, the TENS pulses are delivered within the interval betweenpacing pulses and provide background stimulation to the patient todistract the attention of the patient away from the discomfort caused bythe pacing pulses.

In act 406, a discomfort monitor (e.g., the discomfort monitor 322)prompts for, receives, and records patient feedback regarding the testpattern through a user interface element as described herein. Forexample, the user feedback includes discomfort information acquiredduring execution of the test pattern for subsequent processing. In someexamples, the discomfort information is recorded in data storage (e.g.,the data storage 304 described above with reference to FIG. 3). Thisdiscomfort information may be received as voluntary or involuntary inputfrom the user via the user interface or may be acquired from one or moreother sensors coupled to a sensor interface (e.g., the sensor interface312 described above with reference to FIG. 3). Examples of discomfortinformation received via the user interface include utterances (e.g.,words, moans, groans, crying, or other expressions) and actuation of adiscomfort measuring and/or indicating device (e.g., strain gauge, forcesensor, push or squeeze button, rotary dial, elastic deformable solid).For example, the user can indicate a level of discomfort he or she feelsby actuating any of one or more user interface elements as describedherein. Examples of discomfort information received via other sensors(e.g., motion detection sensors, strain gauges in a garment) includemovements (e.g., tensing of muscles, jerking, shuttering, flinching,changes in respiration) and lack of movement.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for theinput by, for example, presenting a discomfort scale via the userinterface. The discomfort scale may include numeric values and the userinterface may request that the user rate the discomfort experienced onthe numeric scale. The discomfort scale may also include graphicalrepresentations (e.g., faces) and the user interface may request thatthe user rate the discomfort experienced on the graphical scale. In someexamples, the discomfort monitor infers the intensity of the discomfortbased on the amount of pressure detected by the user interface or theperiod of time a user interface element remains actuated. For instance,in one example, the number of seconds that the user interface elementremains actuated equates to a number of the Wong-Baker FACES® PainRating Scale.

In the act 408, the discomfort monitor determines whether the testpattern delivered in the previous iteration of the act 404 was tolerableto the patient. For example, the patient might indicate that the lastadministered test pattern is the maximum discomfort he or she is willingto tolerate by responding to a prompt presented by the user interfacerequesting this information. If the test pattern was tolerable, thetreatment manager proceeds to the act 410. In some examples, ifadditional data is desired and the patient (or caregiver administeringthe baseline process 400) has not aborted the baseline process 400, asame or different (slightly higher or lower level) test pattern can bedelivered to confirm the patient's tolerance level. If the test patternwas not tolerable, the treatment manager proceeds to the act 412. Insome examples, the discomfort monitor determines whether the testpattern was tolerable at least in part by quantifying discomfortinformation. The discomfort information quantified by the discomfortmonitor may have been acquired during execution of the test pattern inthe act 404 or may have been received as voluntary input in response toone or more prompts provided to the user via the user interface withinthe act 406 (i.e., after execution of the test pattern in act 404 iscomplete). In some examples, the discomfort monitor assigns a value tothe discomfort parameter based on the discomfort information. Forinstance, the discomfort monitor may store any of the following valuesas the value of the discomfort parameter: a value of a point on thediscomfort scale selected via user input, a value calculated based on anamount of pressure exerted by the user on an element of the userinterface (e.g., a quartz or ceramic force sensor, or a piezoelectrictransducer), a value calculated based on a period of time a userinterface element is actuated, or a value calculated based on motion ofthe patient or some other involuntary reaction to the test patternexhibited by the patient. For example, in the case of a piezoelectrictransducer, an active element (e.g., a polarized material such as quartz(SiO2) or barium titanate (BaTiO3)) can produce an electric field whenthe element changes dimensions as a result of an imposed mechanicalforce. For example, a force applied to a transducer or force sensor asdescribed herein can be in a range between 0-25 lbs. (110 N). In someexamples, when more force is applied, a resistance of the transducer candecrease.

For example, in the case of a Flexiforce® pressure sensor from Tekscan®,a resistance range changes from substantially open circuit to about 50 kohms. When the force is applied, the resistance measured between leadsof the transducer lowers until it reaches a maximum force value (e.g.,25 lbs). In an implementation, the force applied may be in the form of auser squeezing two opposing surfaces of a sensor. The examples describedherein are not limiting and other kinds of force sensors can be used.

For example, in the case of a ceramic or quartz force sensor, apiezoelectric transduction mechanism can be coupled to a integratedcircuit, e.g., a voltage or charge amplifier. The applied force canproduce a quantity of charge, e.g., Δq. The charge accumulates in thecrystal capacitance and forms a voltage according to the law: ΔV=Δq/C.For example, a low capacitance quartz sensing element can produce a highvoltage output. In such applications, a MOSFET voltage amplifier can beused to control the output voltage. Ceramic sensing elements can exhibita high charge output, and so can be coupled to a charge amplifier.

In the manner described above, a discomfort parameter can be calculatedto correspond to a force sensed by a force sensor. For instance, thediscomfort parameter based on the force sensor can be scaled to bewithin a range of 1-10 units (e.g., the parameter can be configured inaccordance to a predefined numerical relationship to an output voltagelevel of the force sensor).

In some examples, the discomfort monitor determines whether the testpattern was tolerable by comparing the value of the discomfort parameterto a discomfort threshold value. This discomfort threshold value may bea configurable parameter of the medical device that may be adjusted toeach particular patient. For instance, in one example, the discomfortthreshold is set to a value of 4 in the Wong-Baker FACES® Pain RatingScale. Similarly, on the force sensor scale described above, thediscomfort threshold may be set to a value of 5. It is appreciated thatthe patient discomfort scale and threshold as described above can varydepending on the patient's personal preferences and/or the caregiver'srecommendations. For example, the scale employed may be a percentagescale (e.g., 1-100) and a threshold can be set to be 40 percent of fullrange. In some examples, color coded zones may be used to indicate thediscomfort scale, e.g., a red zone corresponding to maximum intensity, ayellow zone corresponding to minimal discomfort, and a green zonecorresponding to discomfort in the middle of the range.

In some examples, the discomfort monitor determines that the testpattern was tolerable where the value of the discomfort parametermaintains a predefined relationship with a discomfort threshold value(e.g., where the value of the discomfort parameter does not transgressthe discomfort threshold value). In these examples, the discomfortmonitor determines that the test pattern was not tolerable where thevalue of the discomfort parameter does not maintain a predefinedrelationship with the discomfort threshold value (e.g. where the valueof the discomfort parameter is equal to or transgresses the discomfortthreshold value). It is appreciated that, depending on the specificcalculations used, a discomfort threshold value may be transgressed by avalue that is greater than or less than the discomfort threshold value.

In act 410, the discomfort monitor adjusts the test pattern. In someexamples, the discomfort monitor adjusts the test pattern by varyingcharacteristics of pulses included in the test pattern. In theseexamples, each characteristic of each pulse may be varied within itsrespective range as described above with reference to the act 404. Ingeneral, the discomfort monitor adjusts one or more characteristicsupward within their respective ranges to increase the efficacy of eachpulse. For instance, in at least one example, the discomfort monitoradjusts each characteristic upward by a step value specified by aconfigurable parameter of the medical device. One effect of thisapproach is to shorten the overall execution time of the baselineprocess 400. Another effect of this approach is to collect fewer testdata points for subsequent analysis. In another example, the discomfortmonitor adjusts only one characteristic upward by the step value. Oneeffect of this approach is to more precisely measure the effect thateach characteristic has on the patient. Another effect of this approachis to collect more test data points for subsequent analysis. In anotherexample, the discomfort monitor adjusts some characteristics upward bythe step value and adjusts others downward by a step value to establishdiscomfort parameter samples for a broad mix of characteristics. It isappreciated that the step values by which each characteristic isadjusted may reside on continuums having different scales. Examples ofthese scales include linear scales, log scales, and exponential scales.

Pacing discomfort may stem from at least two sources: 1) electricalstimulation of the cutaneous nerves; and 2) skeletal muscle contraction,particularly the intercostal muscles. Electrical stimulation can feel toa patient like pin-pricks on the skin, while skeletal muscle contractioncan feel like getting hit in the chest with a hammer or a fist. Inexamples, a degree of cutaneous nerve stimulation can be difficult tomeasure non-invasively but may be easier to ameliorate than the skeletalmuscle contraction. The cutaneous nerve stimulation may be reduced by,for instance, increasing the resistivity of the electrically conductivegel that is against the skin. Thus, some examples as described hereincan include and deploy electrically conductive gel for pacing, such thata resistivity of the gel against the skin can be varied in accordancewith patient discomfort For example, in some implementations, theimpedance as seen by the pacing electrodes can be varied as one of thepacing routine parameters in response to the patient's discomfortmanagement as described herein.

In some example implementations, the device can measure a degree ofskeletal muscle stimulation and use the measurement to determine thediscomfort parameter. For instance, in some examples, the discomfortmonitor uses the value of the measurement as the value of the discomfortparameter. In some examples, the discomfort monitor calculates thediscomfort parameter using the value of the measurement and otherfactors, such as voluntary input as described in detail herein.

In some examples, the discomfort monitor measures the degree of skeletalmuscle contraction using a flexible strain gauge adhered to thepatient's skin. The strain gauge may be composed of, for instance, abi-layer, laminate construction of polyvinylidene fluoride (PVDF), alsosometimes called Kynar. The bi-layer construction generates a voltageinversely proportional to the radius of curvature of the strain gaugelaminate sheet. Thus the electrical voltage generated by the straingauge deformation will be proportional to the degree of intercostalmuscle contractions. Alternatively, the measure of the degree ofintercostal muscle contraction may be accomplished by having at leasttwo motion sensors such as micro-electro-mechanical systems (MEMS)accelerometers affixed to adjacent ribs and the relative motion measuredin, e.g., the 0-500 millisecond, time period subsequent to theelectrical pulse.

The patient may also enter a perceived discomfort via the userinterface, which is configured to receive this input. In these examples,the discomfort monitor can be configured to store the two values: e.g.,the patient-perceived discomfort on the discomfort scale and themeasured skeletal muscle contraction. This sampling can be repeated fortwo or more pacing parameters to create a series of two or more vectorscomposed of at least a perceived discomfort score (PDS) and a measure ofskeletal muscle contraction (SMC). In these examples, the discomfortmonitor generates a lookup table from the multiple values of PDS/SMCvectors that were generated using the multiple instances of pacingparameters. The pacing parameter may be pacing current, with the PDS/SMCvector pairs generated, for instance, at 10-100 mA in 10 mA increments.An example of such a lookup table is shown below:

Current 10 20 30 40 50 60 70 80 90 100 PDS 0 2 5 6 8 9 10 10 10 10 SMC0.35 1.2 1.7 2.3 2.7 3.2 5.6 7.7 9.2 11.3

Thus, where the wearable medical device determines that the patient isin need of pacing, the wearable medical device initiates pacing with thepacing current amplitude that corresponds to a low level of perceiveddiscomfort of that particular patient. The correspondence of PDS and SMClevels with changes in pacing amplitude or other parameters can varyfrom patient to patient. As such, an initial baselining process can beused to calibrate the pacing parameter values with a particularpatient's perception of discomfort.

Next, the wearable medical device checks a patient physiologicalparameter, such as the ECG or pulse oximetry. In some examples, thewearable medical device checks the physiological parameter by analyzinginformation transmitted by another wearable device, such as an iWatch(from Apple, Inc., of Cupertino Calif.), that is in wirelesscommunication with the wearable medical device via the sensor interface.Through this analysis, the wearable medical device determines whetherpacing has been effective and is, therefore, generating blood flow. Ifthe pacing is effective, then the wearable medical device identifies thecurrent pacing parameter values as being an effective level for pacingthat is still comfortable for the patient.

If, however, a pulse or other measure of pacing effectiveness is notdetected in one or more of the physiological parameter measurements,then the wearable medical device increases the amplitude of a pacingparameter, for example, pacing current, to the next setting. This willlikely result in a higher level of discomfort but also a higher chanceof being effective. The wearable medical device may repeat this processuntil pacing effectiveness has been achieved. More elaborate searchmethods may be employed, such as a binary search, to minimize the amountof time required to achieve effective pacing.

Alternatively, instead of a lookup table, the wearable medical devicemay generate a mathematical relationship—the “discomfort estimationfunction” (DEF)—between the pacing parameters, SMC, and an estimate ofdiscomfort. The mathematical relationship may be interpolation of thedata points in the lookup table. The interpolation may be linear ornonlinear as well as employ splines. The wearable medical device maygenerate the mathematical relationship using one or more techniques suchas logistic regression, neural networks, or fuzzy logic.

It has been found that patient's perceptions of discomfort shift withvarying external circumstances as well as internal mental and emotionalstatus. In another embodiment, the wearable medical device estimates thepatient's actual discomfort level by analyzing the SMC measurements inreal time (or near real time) while pacing is occurring.

In some examples, the user interface includes one or more elements thatreceive input indicating the discomfort level being experienced by thepatient during actual pacing process execution, rather than as a resultof operating in a baseline or test mode. In these examples, thediscomfort monitor stores these discomfort levels for a particular setof pacing parameters during actual pacing as a secondary, calibratingset that modifies the original discomfort levels acquired during thebaseline process 400. The wearable medical device can use theseadditional data points to provide a more accurate DEF estimate. Forinstance, the wearable medical device may store the data points andcalculate a new DEF in real time (or near real time). In some examples,the wearable medical device may transmit the actual pacing discomfortlevels to a server and database that stores the results for that patientas well as many other patients. In these examples, the server mayexecute the optimization and download new pacing parameter values to thewearable medical device at some point after the clinical event.

In act 412, the discomfort monitor uses the test data to determinebaseline values for the pacing parameters. In an example, the discomfortmonitor can select the baseline pacing parameter values for the patientbased on a predetermined relationship (e.g., a formula) between thepatient's range of discomfort parameters, the threshold discomfort, andunderlying pacing parameters. For example, the baseline pacing parametervalues can be the pacing parameter values corresponding to a discomfortparameter value that is a fraction of the patient's discomfort thresholdvalue, e.g., 25-75% of the patient discomfort threshold.

In some implementations, the baseline pacing parameter values can beselected without reference to the patient's discomfort threshold. Forexample, the baseline pacing parameter values can be a set of valuesselected at a lower (minimum) bound of the ranges of values for thepacing parameters. For example, the baseline pacing parameter values canbe a set of values selected at a lower (minimum) bound of the ranges ofvalues for a first set of pacing parameters (e.g., pulse amplitude andpulse width), and a values selected around a middle of the range ofvalues for a second set of pacing parameters (e.g., pulse rate and/orpulse duty cycle). It is appreciated that the baseline pacing parametervalues can be selected by any process reflecting the patient's toleranceand are not limited to the examples described above. In some cases,where a baseline process 400 is not available, a set of values can beselected as default values in accordance with the principles describedherein.

In some implementations, the baseline process 400 may set values foronly a subset of the parameters. For example, the baseline process 400may set values for only an amplitude and a pulse width. The remainingparameters may either be assigned default values in accordance with theprinciples described herein, or the manually provided by the patientand/or caregiver, e.g., via a user interface.

In one example, the discomfort monitor determines the baseline values ofthe pacing parameters by solving an optimization problem. In thisexample, the discomfort monitor maximizes the efficacy of each pacingroutine executable by the treatment manager subject to the rangeconstraints described with reference to the act 404 above and subject tothe value of the discomfort parameter maintaining a predefinedrelationship with to the discomfort threshold value.

For instance, according to one example, for all pacing pulses 1 to n ina pacing routine p, let the following variables represent the followingcharacteristics of pacing pulses and TENS pulses, where 1≤i≤n. It isappreciated that each of the pacing and TENS pulse characteristics inTable 1 and Table 2 below may be controlled by a pacing parameter set bythe medical device controller (e.g., controlled by treatment manager 314of medical device controller 300).

TABLE 1 Variable Pacing Pulse Characteristic a_(i) amplitude of pulse iw_(i) width of pulse i r_(i) rate of pulse i v_(i) waveform of pulse ip_(i) period of pulse i d_(i) duty cycle of pulse i c_(i) ramp timeconstant of pulse i

TABLE 2 Variable TENS Pulse Characteristic x_(i) amplitude of pulse iy_(i) width of pulse i z_(i) rate of pulse i q_(i) waveform of pulse iGiven these variables, the optimization problem to maximize the efficacyof the baseline parameters may be formulated as follows: maxΣ_(i=1) ^(n)f(i), where f(i) is the efficacy of a pacing pulse resulting from thecombination of pacing pulse characteristics (a_(i), w_(i), r_(i), v_(i),p_(i), d_(i), c_(i)); subject to:

d(i)≤t for all i, where d(i) is the discomfort parameter resulting fromthe pacing pulse characteristics (a_(i), w_(i), r_(i), v_(i), p_(i),d_(i), c_(i)) in combination with the TENS pulse characteristics (x_(i),y_(i), z_(i), q_(i)) and t is the value of the discomfort threshold;

15 milliamps≤a_(i)≤200 milliamps;

0.5 milliseconds≤w_(i)≤40 milliseconds;

20 pacing pulses per minute≤r_(i)≤200 pacing pulses per minute;

20 microseconds≤p_(i)≤500 microseconds;

10 percent≤d_(j)≤100 percent;

40 microseconds≤c_(i)≤100 microseconds;

v_(i) ∈ {rectilinear, pulse train, truncated exponential, variable,biphasic};

0 milliamps≤x_(i)≤200 milliamps;

0.001 milliseconds≤y_(i)≤0.5 milliseconds;

0.5 pulses per minute≤z_(i)≤500 pulses per minute; and

v_(i) ∈ {rectilinear, pulse train, biphasic};

In some examples, the discomfort monitor approximates d(i) by fitting amathematical function to the test data recorded during the act 406 (by,for example, logistic regression analysis). In these examples, thediscomfort monitor uses the fitted expression as a constraint in theoptimization problem as described above and solves the optimizationproblem to generate a set of baseline parameter values (a_(b), w_(b),r_(b), v_(b), P_(b), d_(b), c_(b), x_(b), y_(b), z_(b)) for each pacingroutine p executable by the treatment manager. The baseline process 400ends after execution of the act 412.

Processes in accord with the baseline process 400 enable patients toestablish an individualized set of baseline values for the pacingparameters. The processes enable execution of tolerable external pacingroutines, thereby providing patients with a measure of control notafforded by conventional external pacing processes. Accordingly, thepatient may initially be administered a pacing routine in accordancewith the established baseline values (e.g., as a set of default valuesfor the pacing parameters). The patient may then control the pacingparameters through one or more user interface elements as describedherein. In the event the patient is unable to provide voluntaryfeedback, the medical device can use other sensor information todetermine and evaluate the efficacy of the pacing routine as describedherein.

In some examples, the optimization problem described above may beapplied to test data that represents a population of patients todetermine baseline values for the “average” patient. These “average”baseline values may be stored as default values to be used where thebaseline process 400 has not been executed or where the baseline process400 is not available to be performed for a patient prior to commencementof patient monitoring.

In one example, the following baselining procedure may be employed.

First, set pace pulse width to 75 ms, no TENS, pace pulse ramp tominimum (e.g. 0.01 milliseconds). These settings provide for maximumeffectiveness of pace pulse.

Second, for pace pulse amplitudes from 10 mA to 150 mA in increments of10 mA, check to see if there is pace pulse capture and obtain thediscomfort measure from the patient for each mA setting.

Third, for the pace current setting that is at least 20 mA higher thanthe first setting at which pacing capture was detected (“test pacecurrent setting”), adjust the pace ramp from the minimum ramp to a rampof 75 ms in steps of 15 ms. Assess for pace capture at each setting andthe user's assessment of the discomfort measure. Ramp time for step 4(“test ramp time”) below is the ramp time value for which there has beenno loss of pace capture and results in the least amount of patientdiscomfort.

Fourth, setting the device to the test pace current setting and the testramp time, decrease the pace pulse width from 75 ms down to 5 ms inincrements of 10 ms. The “test pace pulse width” is the pace pulse widththat is 20 ms larger than the minimum pulse width where capture wasstill achieved.

Using the test pace current setting, test ramp time, and test pace pulsewidth, determine the response of the discomfort measure to variation inthe TENS parameters.

FIG. 17 illustrates an example baseline process 1700 in accordance withan implementation based on the above process. For example, the baselineprocess 1700 begins at 1702 where the discomfort monitor (e.g.,discomfort monitor 322 of treatment manager 314 of FIG. 3) sets thepacing pulse width to 75 milliseconds, sets the pacing pulse ramp tominimum (e.g. 0.01 milliseconds), and sets the active TENS routine tonone (e.g., no TENS pulses). In implementations, such settings canprovide for maximum effectiveness of the pacing routine.

In act 1704, the discomfort monitor increases the pacing pulse amplitudeby a predetermined amount, e.g., in increments of 10 mA. In someimplementations, both or either of the initial pacing pulse amplitudeand the predetermined increment in the pacing pulse amplitude can begoverned by user-configurable parameters. For example, a default valuefor the initial pacing pulse amplitude of 10 mA can be programmed intothe device (either during the initial device configuration or prior toshipping the device to the caregiver). Similarly, a default value forthe increment in pacing pulse amplitude of 10 mA can be programmed intothe device. In implementations, the caregiver may be able to modifythese values for his or her patient. Once the initial pacing pulseamplitude value is set, the discomfort monitor can gradually increasethe amplitude according to the predetermined increment values. Forexample, the discomfort monitor can increase the pacing pulse amplitudeby 10 mA in each iteration. In some examples, the discomfort monitor canbe configured to change the increment value for one or more iteration.For instance, after about 10-12 iterations, the discomfort monitor mayincrease the amplitude by only 5 mA for each successive iteration.

In act 1706, the wearable medical device delivers one or more pacingpulses in accordance to the pacing routine parameters set in acts1702-04. For example, the device may be configured to deliver apreconfigured number of pulses (e.g., 1-3 or more pulses).

In act 1708, the discomfort monitor records discomfort information inaccordance with the principles described herein. Further, the cardiacmonitor records capture information, e.g., checks to see if there ispacing pulse capture using one or more techniques described herein. Therecorded information is associated with the pulse amplitude and eitherstored locally (e.g., on a memory disposed within the device, such as,data storage 304 of FIG. 3) or transmitted to a remote processing site.

In act 1710, the discomfort monitor determines whether the pacing pulseamplitude is equal to a predetermined maximum amplitude value, e.g., 150milliamps If the pacing pulse amplitude is not equal to thepredetermined maximum amplitude value of 150 milliamps, the discomfortmonitor returns to the act 1704. If the pacing pulse amplitude is equalto the predetermined maximum amplitude value of 150 milliamps, thediscomfort monitor proceeds to act 1712.

In act 1712, the discomfort monitor determines the baseline pacing pulseamplitude by identifying the first pacing pulse amplitude that resultedin capture and adding a certain current value, e.g., at least 20milliamps, to the identified pacing pulse amplitude. Also in act 1712,the discomfort monitor sets the pacing pulse amplitude to the determinedbaseline pacing pulse amplitude, e.g., the test pace current settingreferenced above.

In act 1714, the discomfort monitor increases the pacing ramp time by apredetermined amount, e.g., 15 microseconds.

In act 1715, the wearable medical device delivers one or more pacingpulses and in act 1717, the discomfort monitor records discomfortinformation and the cardiac monitor records capture information.

In act 1718, the discomfort monitor determines whether the pacing ramptime is equal to a predetermined maximum ramp time value of, e.g., 75microseconds. If the pacing ramp time is not equal to the predeterminedmaximum ramp time value of 75 microseconds, the discomfort monitorreturns to the act 1714. If the pacing ramp time is equal topredetermined maximum ramp time value of 75 microseconds, then thediscomfort monitor proceeds to act 1720.

In the act 1720, the discomfort monitor determines the baseline ramptime by identifying the ramp time value for which there was no loss ofpacing capture and for which the patient experiences the least amount ofdiscomfort. Also in the act 1720, the discomfort manager sets ramp timeto the determined baseline ramp time value, e.g., the test ramp timereferenced above.

In act 1722, with the device set to the test pace current setting andthe test ramp time in accordance with the acts described above, thediscomfort manager decreases the pacing pulse width by a predeterminedamount, e.g., 10 microseconds. For example, the initial pacing pulsewidth is set to be 75 ms, and is decreased in the aforementioned stepsof 10 ms to a minimum pacing pulse width value of 5 ms. In act 1723, thewearable medical device delivers one or more pacing pulses. In act 1724,the cardiac monitor determines whether the pacing pulses resulted incapture. If the pacing pulses resulted in capture, the discomfortmonitor returns to the act 1722. If the pacing pulses did not result incapture, the discomfort monitor determines the baseline pulse widthvalue, e.g., the test pace pulse width, by identifying a smallest pacingpulse width that resulted in capture and adding a predetermined value,e.g., 20 milliseconds, to the identified pacing pulse width.

In act 1728, with the device set to the above test pace current setting,test ramp time, and test pace pulse width in accordance with the actsdescribed above, the discomfort manager applies TENS routines withvarious parameters as described above, acquires and records discomfortinformation for each, and identifies the TENS routine parameters thatare associated with the least patient discomfort.

From the set of data generated from the baseline process 1700 above, amathematical function can be derived that describes the relationshipbetween the pacing parameters (including, in some implementations, theTENS parameters) and both discomfort and pacing effectiveness, and knownstatistical methods such as response surface methodology and logisticregression can be used to find the optimal trade-off between minimizingdiscomfort and maximizing pacing effectiveness. In one example, aprocess such as response surface methodology (RSM) can be used toexplore the relationships between several explanatory variables and oneor more response variables in implementing a pacingeffectiveness/patient discomfort program. For example, a sequence ofdesigned experiments can be used to obtain an optimal response using atleast a second-degree polynomial model. For example, a first-degreepolynomial model can be used to determine which explanatory variablesmay have an impact on the response variables of interest. A morecomplicated design, such as a central composite design, can beimplemented to estimate a second-degree polynomial model for use in theoptimization of the parameters as described herein (e.g. to maximize,minimize, or attain a specific target for the parameters).

Example Pacing Management Process

As described above, various examples implement processes through which amedical device manages discomfort experienced by a patient duringexecution of a pacing routine. FIG. 5 illustrates one such pacingmanagement process 500. As shown, the pacing management process 500includes acts of receiving signals, analyzing the received signals,determining whether the analyzed signals represent a normal cardiacrhythm, identifying a pacing routine to treat an arrhythmia, loadingbaseline pacing parameters associated with the patient and theidentified pacing routine, and managing execution of the identifiedpacing routine.

In act 502, the treatment manager receives electrode signals generatedfrom detectable characteristics of the patient's cardiac function viaone or more electrodes (e.g., the electrode pairs 326 and 328 describedabove with reference to FIG. 3). In act 504, the treatment manageranalyzes the received signals using a cardiac monitor (e.g., the cardiacmonitor 320 described above with reference to FIG. 3).

In act 506, the cardiac monitor determines whether the patient's cardiacrhythm is normal. If so, the pacing management process 500 returns tothe act 502. Otherwise, the cardiac monitor identifies an arrhythmia inact 508. In act 510, the treatment manager determines whether theidentified arrhythmia is treatable by either a defibrillating shock or apacing routine. Where the treatment manager detects an arrhythmia thatrequires defibrillation, the treatment manager may begin adefibrillation treatment protocol potentially culminating in adefibrillating shock. Where the treatment manager determines that theidentified arrhythmia is treatable by an identified pacing routine(e.g., from the pacing routines 324 described above with reference toFIG. 3), the treatment manager proceeds to act 512. The treatmentmanager may determine that the identified arrhythmia is treatable by theidentified pacing routine by, for example, referring to one or moreconfigurable parameters stored in a data storage (e.g., the data storage304 described above with reference to FIG. 3) that associatesarrhythmias to pacing routines.

In the act 512, the treatment manager loads baseline pacing parametersassociated with the patient and identified pacing routine. Thesebaseline pacing parameters may identify a TENS routine (e.g., from theTENS routines 334 described above with reference to FIG. 3) to beexecuted in conjunction with the identified pacing routine. Asillustrated in FIG. 5 by dashed lines, the act 512 is optional and maynot be executed in some examples where the baseline process 400 has beenomitted. For example, as indicated below, if a baseline process was notcompleted, then default values can be used for the parameters of thepacing routine.

In the act 514, the treatment manager executes the identified pacingroutine and any associated TENS routines as described below withreference to FIGS. 6-8 and 16 and the pacing management process 500ends. The pacing management process 500 may execute repeatedly duringoperation of the medical device to monitor and treat the patient asneeded. The following sections describe processes that may be executedwithin the act 514.

Example Direct Control Pacing Process

In one example of the act 514, the treatment manager is configured toprovide the patient with direct control of a pacing routine. FIG. 16illustrates one example of a managed pacing routine 1600 that isexecuted within the act 514. The managed pacing routine 1600 executes adirect control pacing process that is managed to decrease discomfortrelative to conventional pacing processes. As shown in FIG. 16, themanaged pacing routine 1600 includes acts of delivering pacing pulses,calculating a discomfort parameter, adjusting pacing parameters, anddetermining whether pacing should continue.

In act 1602, the treatment manager delivers one or more pacing pulsesand monitors patient discomfort. In some examples, the treatment managerdelivers the one or more pacing pulses to the patient according to thebaseline parameters loaded in the act 512 described above with referenceto FIG. 5. In examples where the act 512 has been omitted, the treatmentmanager delivers one or more pacing pulses to the patient in accord withdefault pacing parameters stored in the data storage. In at least oneexample, the default pacing parameter values are each set at the upperbound (maximum) of each range of values. In some examples, the defaultpacing parameter values may be a set of values selected at a lower(minimum) bound of the ranges of values. In some examples, the defaultpacing parameter values may be a set of values selected at a lower(minimum) bound of the ranges of values for a first set of pacingparameters (e.g., pulse amplitude and pulse width), and a valuesselected around a middle of the range of values for a second set ofpacing parameters (e.g., pulse rate and/or pulse duty cycle). It isappreciated that one or more combinations of default pacing parametervalues for each pacing parameter can be selected. In someimplementations, rather than automatically using default values, thetreatment manager can prompt the user (e.g., patient and/or caregiver)to provide initial values for the pacing parameters via the userinterface. For example, the user interface element may provide asuggested range of values and prompt the user to select from within therange. In some instances, the user may be able to override the defaultpacing recommendations and provide his or her own preferences for pacingparameters.

In some examples, the user may be prompted to specify an initialdiscomfort threshold value, which the treatment manager can use todetermine the optimum pacing parameters, e.g., using the optimizationprocess described above. In an implementation, the user can change apreviously stored baseline and/or default discomfort threshold value, orchange any of the baseline and/or default pacing parameter values.

In the act 1602, the one or more pacing pulses may be delivered inconjunction with one or more TENS pulses executed according to a TENSroutine associated with the pacing routine 1600. In at least someexamples, the TENS pulses are delivered between pacing pulses, e.g., todistract the patient and further reduce the discomfort experienced bythe patient during the pacing routine 1600.

In act 1604, the discomfort monitor prompts for, receives, and recordsdiscomfort information and records any discomfort information acquiredduring execution of the pacing pulses for subsequent processing. In someexamples, the discomfort information is recorded in the data storage.This discomfort information may be received as voluntary input from theuser via the user interface. Examples of discomfort information receivedvia the user interface include utterances (e.g., words, moans, groans,crying, or other expressions) and actuation of a discomfort measuringand/or indicating device (e.g., strain gauge, button, rotary dial,elastic deformable solid). For example, the user can indicate a level ofdiscomfort he or she feels by actuating any of one or more userinterface elements as described herein.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for theinput by, for example, presenting a discomfort scale via the userinterface. The discomfort scale may include numeric values and the userinterface may request that the user rate the discomfort experienced onthe numeric scale. The discomfort scale may also include graphicalrepresentations (e.g., faces) and the user interface may request thatthe user rate the discomfort experienced on the graphical scale. In someexamples, the discomfort monitor infers the intensity of the discomfortbased on the amount of pressure detected by the user interface or theamount of time a user interface element remains actuated. For example,in a manner similar to that outlined above for the baseline process, thevoluntary input may be in the form of actuation of one or more userinterface elements, such as a force sensor (e.g., piezoelectric, quartz,or ceramic based transducer), a push or squeeze button, a rotaryspring-loaded dial, or an elastic deformable solid.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for a changein input where the input has not changed state for a time period greaterthan a value of a timeout configurable parameter of the medical device.In this way, these examples prevent involuntary input received asvoluntary input from affecting the behavior of the medical device for atime period greater than the timeout.

Also in the act 1604, the discomfort monitor calculates a discomfortparameter that quantifies the discomfort information. This discomfortinformation quantified by the discomfort monitor may have been voluntaryinput acquired during execution of the pacing pulses in the act 1602 ormay have been received as voluntary input in response to one or moreprompts provided to the user via the user interface within the act 1604.In some examples, the discomfort monitor assigns a value to thediscomfort parameter based on the discomfort information using one ormore of the mechanisms described herein (e.g., the mechanisms describedabove with reference to the act 408 of FIG. 4). For instance, thediscomfort monitor may store any of the following values as the value ofthe discomfort parameter: a value of a point on the discomfort scaleselected via user input, a value calculated based on an amount ofpressure exerted by the user on an element of the user interface, or avalue calculated based on motion of the patient or some other voluntaryaction exhibited by the patient and detected by the medical device. Forexample, the discomfort monitor may cause the medical device to displaythe value of the discomfort parameter to the user during administrationof the pacing routine. As noted above, a user interface may display thediscomfort information, for example, in the form of a numerical scale(e.g., 1-10 scale, or percentage scale) or a color coded band of zones.

In act 1606, the discomfort monitor dynamically adjusts the pacingparameters in response to the patient's input. Accordingly, where thepatient is conscious and actively contributing discomfort information(e.g., by providing feedback about discomfort substantially in real timeand during the administration of the pacing routine), the discomfortmonitor determines the adjusted pacing parameters based on apredetermined relationship between the pacing parameters and thediscomfort parameter. For instance, where discomfort parameter indicatesa conscious patient experiencing a high degree of discomfort, thediscomfort monitor may adjust the pacing parameters to deliver no pacingpulses, or only background TENS pulses. Conversely, where the discomfortparameter indicates a conscious patient is experiencing little or nodiscomfort, and pacing is still required, the discomfort manager mayadjust the pacing parameters to deliver pacing pulses with higherefficacy (e.g., by increasing, among other parameters, rate, width,and/or amplitude) in accordance with the principles described herein.

In one example, the range of each pacing parameter within a pacingroutine is inversely mapped to a range including all possible values ofthe discomfort parameter, with lower pacing parameter valuescorresponding to higher discomfort parameters. In this example, thediscomfort manager converts the discomfort parameters to pacingparameters using the inverse map, thereby decreasing pacing parameters(and associated discomfort) in direct portion to the intensity ofdiscomfort reported by the patient.

In act 1608, the treatment manager receives (via the one or moreelectrodes) and analyzes (via the cardiac monitor) electrode signalsgenerated from detectable characteristics of the patient's cardiacfunction. During the analysis, the cardiac monitor determines whetherthe patient's current cardiac condition warrants further pacing. If so,the treatment manager returns to the act 1602 and continues execution ofthe pacing routine 1600. If the cardiac monitor determines that thepatient's current cardiac condition does not warrant further pacing(e.g., determines that a normal sinus rhythm has returned), the pacingroutine 1600 ends. In some examples, upon termination of the pacingroutine 1600, the treatment manager returns to the process 500 andcontinues to monitor the patient's physiological signals, such as thepatient's ECG, temperature, pulse oxygen level, respiration, etc.

Processes in accord with the managed pacing routine 1600 enable patientsto control parameters of pacing routines via immediate feedback providedvia a user interface element, thereby enabling patients to activelymanage discomfort associated with external pacing processes.

In one example, the patient may not control the pacing (including TENS)parameters individually, but rather controls the degree to which thewearable medical device trades off effectiveness of a pacing routineagainst discomfort. For instance, the wearable medical device maydetermine, as a result of the baseline process that the patient respondsparticularly well to increases in pacing ramp time.

For example, the wearable medical device may determine that the patientis responding well based on a parameter indicating that there are largerchanges (system gain) in patient discomfort levels for a particularchange in the pacing parameter (e.g., ramp time), and at the same timesmaller changes (system gain) in pacing effectiveness for a particularchange in the pacing parameter (e.g., ramp time). In some examples, sucha parameter can be based on optimizing for either a difference or ratioof these two system gains. For example, such a difference or ratio maybe in the form of a “parameter efficiency.” These system gains can beestimated in the slopes of the particular parameter on the responsesurface or the coefficients of the logistic regression or otherstatistical model.

In one example, the pacing parameters can be changed at the same time insteps for each user request to decrement the pacing discomfort. Forexample, the step sizes for each parameter can be proportional to apredetermined parameter efficiency. In some cases, the parameter withthe highest parameter efficiency can be changed first until there issome loss in pacing capture of the patient, at which point the pacingparameter with the next highest parameter efficiency can be changed inincrements. In this manner, the process can be repeated in apredetermined sequence for the remaining parameters.

In some examples, the TENS parameters can be changed in a similarfashion as described above either along with or after other pacing pulseparameters have been set. This results in the changes following along anoptimal trajectory along the response surface, minimizing pacingdiscomfort while maximizing pacing effectiveness.

For example, the response surface may be dynamic depending on thepatient's mental or physiologic status or external circumstances.Accordingly, in some embodiments, though the patient may be capable ofadjusting the pacing parameters to reduce discomfort, the reduction maybe temporary, as a reduction in discomfort may introduce some increasein the level of pacing effectiveness. In one scenario, patient-initiatedreduction in discomfort could cause a pacing routine to no longer beeffective. As such, if user input is provided by the patient that thediscomfort is perceived to be too high, then the discomfort monitor canmodify one or more of the pacing parameters to decrease the patientdiscomfort. Assuming that the original settings provided maximum pacingeffectiveness, after a predetermined period of time of e.g., about 5seconds to 5 minutes, the device can begin to revert all the modifiedpacing parameters to their original, more effective settings. In thisfashion, if the patient loses consciousness because the pacing wasineffectiveness in generating sufficient blood flow, then the device canautomatically revert to a life-sustaining (albeit uncomfortable) pacingparameter settings. In some examples, the pacing parameters may bemodified in such a fashion that the pacing remains optimally effectiveduring the course of the parameter modifications. In some examples,maintaining optimal effectiveness during the course of parametermodification may take the form of having the parameter changes followthe response surface determined during prior testing and baselining ofthe patient, or of multiple patients.

In some implementations, the pacing parameter settings may be regulatedby a pressure sensitive input, such that, as long as the patient issqueezing the pressure (or force) sensitive input with at least somepredetermined threshold level of pressure (or force) then the devicewill not continue to revert to the original settings.

In some implementations, the pressure sensing may be continuous orsubstantially continuous, and the patient themselves can autoregulatetheir pacing parameter settings as described herein.

Fixed Rate and Energy Pacing

In accordance with one example of the act 514, the treatment manager isconfigured to manage patient discomfort while pacing the heart of apatient at a fixed rate and fixed energy. Fixed rate and energy pacingmay be appropriate in response to various types of cardiac arrhythmias.Examples of these types of cardiac arrhythmias include bradycardia, alack of sensed cardiac activity (spontaneous or post shock asystole),and pulseless electrical activity. In some cases, these cardiacarrhythmias may occur before or after one or more defibrillation shocks.For example, the treatment manager may be configured to provide pulsesat a fixed energy level, a fixed pulse width, and a fixed frequency inresponse to detection of any of the above-noted events via the ECGsensing electrodes. The energy level of the pacing pulses may be set toa fixed value by applying a desired current waveform for a determinedduration of time by one or more of the plurality of therapy electrodes.

FIG. 6 illustrates one example of a managed pacing routine 600 that isexecuted within the act 514. The managed pacing routine 600 executes afixed rate and energy pacing process that is managed to decreasediscomfort relative to conventional pacing processes. As shown in FIG.6, the managed pacing routine 600 includes acts of delivering pacingpulses, calculating a discomfort parameter, adjusting pacing parameters,and determining whether pacing should continue.

In act 602, the treatment manager delivers one or more pacing pulses tothe patient according to the baseline parameters loaded in the act 512described above with reference to FIGS. 5 and 16. In examples where theact 512 has been omitted, the treatment manager delivers one or morepacing pulses to the patient in accord with default pacing parametersstored in the data storage. In the act 602, the one or more pacingpulses may delivered in conjunction with one or more TENS pulsesexecuted according to a TENS routine associated with the pacing routine600.

In act 604, the discomfort monitor prompts for, receives, and recordsdiscomfort information and records any discomfort information acquiredduring execution of the pacing pulses for subsequent processing. In someexamples, the discomfort information is recorded in the data storage.This discomfort information may be received as voluntary or involuntaryinput from the user via the user interface or may be acquired from oneor more other sensors coupled to a sensor interface. Examples ofdiscomfort information received via the user interface includeutterances (e.g., words, moans, groans, crying, or other expressions)and actuation of a discomfort measuring and/or indicating device (e.g.,strain gauge, button, rotary dial, elastic deformable solid). Forexample, the user can indicate a level of discomfort he or she feels byactuating any of one or more user interface elements as describedherein. Examples of discomfort information received via other sensors(e.g., motion detection sensors, strain gauges in a garment) includemovements (e.g., tensing of muscles, jerking, shuttering, flinching,changes in respiration) and lack of movement.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for theinput by, for example, presenting a discomfort scale via the userinterface. The discomfort scale may include numeric values and the userinterface may request that the user rate the discomfort experienced onthe numeric scale. The discomfort scale may also include graphicalrepresentations (e.g., faces) and the user interface may request thatthe user rate the discomfort experienced on the graphical scale. In someexamples, the discomfort monitor infers the intensity of the discomfortbased on the amount of pressure detected by the user interface or theamount of time a user interface element remains actuated. For example,in a manner similar to that outlined above for the baseline process, thevoluntary input may be in the form of actuation of one or more userinterface elements, such as a force sensor (e.g., piezoelectric, quartz,or ceramic based transducer), a push or squeeze button, a rotaryspring-loaded dial, or an elastic deformable solid.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for a changein input where the input has not changed state for a time period greaterthan a value of a timeout configurable parameter of the medical device.In this way, these examples prevent involuntary input received asvoluntary input from affecting the behavior of the medical device for atime period greater than the timeout.

In the act 606, the discomfort monitor determines whether the pacingpulses delivered in the previous iteration of the act 602 were tolerableto the patient based on any of the mechanisms described herein. If thepacing pulses were tolerable, the treatment manager proceeds to the act610. If the pacing pulses were not tolerable, the treatment managerproceeds to the act 608. In some examples, the discomfort monitordetermines whether the pacing pulses were tolerable at least in part byquantifying discomfort information. This discomfort informationquantified by the discomfort monitor may have been acquired duringexecution of the pacing pulses in the act 602 or may have been receivedas voluntary input in response to one or more prompts provided to theuser via the user interface within the act 604 (i.e., after execution ofthe pacing pulses in act 602 is complete). In some examples, thediscomfort monitor assigns a value to the discomfort parameter based onthe discomfort information using one or more of the mechanisms describedherein (e.g., the mechanisms described above with reference to the act408 of FIG. 4). For instance, the discomfort monitor may store any ofthe following values as the value of the discomfort parameter: a valueof a point on the discomfort scale selected via user input, a valuecalculated based on an amount of pressure exerted by the user on anelement of the user interface, or a value calculated based on motion ofthe patient or some other involuntary reaction to the pacing pulsesexhibited by the patient.

In some examples, the discomfort monitor determines whether the pacingpulses were tolerable by comparing the value of the discomfort parameterto a discomfort threshold value. This discomfort threshold value may bea configurable parameter of the medical device. In some examples, thediscomfort monitor determines that the pacing pulses were tolerablewhere the value of the discomfort parameter maintains a predefinedrelationship with to the discomfort threshold value (e.g., where thevalue of the discomfort parameter does not transgress the discomfortthreshold value). In these examples, the discomfort monitor determinesthat the pacing pulses were not tolerable where the value of thediscomfort parameter does not maintain a predefined relationship withthe discomfort threshold value (e.g. where the value of the discomfortparameter is equal to or transgresses the discomfort threshold value).It is appreciated that, depending on the specific calculations used, adiscomfort threshold value may be transgressed by a value that isgreater than or less than the discomfort threshold value.

In act 608, the discomfort monitor adjusts the pacing parameters. Insome examples, the discomfort monitor determines the adjusted pacingparameters substantially in real time based on immediate feedback fromthe patient as described above with reference to FIG. 16.

In some examples, where voluntary feedback is unavailable (e.g., thepatient is unable to provide dynamic feedback regarding his or her levelof discomfort) the discomfort monitor determines the adjusted pacingparameters in a similar manner as outlined above with respect to thebaseline process 400 by solving an optimization problem similar to theoptimization problem described above with reference to described abovewith reference to act 412 of FIG. 4. However, the optimization problemsolved within the act 608 replaces these constraints:

15 milliamps≤a_(i)≤200 milliamps;

0.5 milliseconds≤w_(i)≤40 milliseconds; and

20 pacing pulses per minute≤r_(i)≤200 pacing pulses per minute with thefollowing constraints:

a_(i)=a_(b) (or the value of a configurable parameter set for fixedenergy and rate pacing);

w_(i)=w_(b) (or the value of a configurable parameter set for fixedenergy and rate pacing); and

r_(i)=r_(b) (or the value of a configurable parameter set for fixedenergy and rate pacing). In addition, the discomfort monitor improvesany approximation of the function d(i) by incorporating the datapoint(s) generated in act 606.

In act 610, the treatment manager receives (via the one or moreelectrodes) and analyzes (via the cardiac monitor) electrode signalsgenerated from detectable characteristics of the patient's cardiacfunction. The cardiac monitor determines whether the patient's currentcardiac condition warrants further pacing. If so, the treatment managerreturns to the act 602 and continues execution of the pacing routine600. If the cardiac monitor determines that the patient's currentcardiac condition does not warrant further pacing (e.g., determineswhether a normal sinus rhythm has returned), the pacing routine 600ends. In some examples, upon termination of the pacing routine 600, thetreatment manager returns to the process 500 and continues to monitorthe patient's physiological signals, such as the patient's ECG,temperature, pulse oxygen level, respiration, etc.

During an initial fitting of a medical device that may execute the fixedrate and energy pacing routine 600, the level of current (pulseamplitude), the pulse width, and the frequency (rate) of the pulses maybe set to an appropriate level based on the input of a medicalprofessional (such as the patient's cardiologist) and the physiologicalcondition of the patient (e.g., based on the patient's normal restingheart rate, the patient's thoracic impedance, etc.) In some examples,the level of current, the pulse width, and the frequency of the pulsesmay simply be set to an appropriate value based on typical impedancevalues for an adult or child, and typical resting heart rates for anadult or child. This initial fitting may be performed in accord with theact 402 described above with reference to FIG. 4 or otherwise.

It should be appreciated that because pacing at a fixed rate mayinterfere with the patient's own intrinsic heart rate, the treatmentmanager can be configured to perform such fixed rate and energy pacingonly in the event of a life-threatening bradycardia, a lack of anydetected cardiac activity following shock, or in response to pulselesselectrical activity following a shock.

Processes in accord with the managed pacing routine 600 enable patientsto control parameters of pacing routines via feedback provided to a userinterface, thereby enabling patients to actively manage discomfortassociated with external pacing processes.

Demand (Adjustable Rate) Pacing

In accordance with one example of the act 514, the treatment manager isconfigured to manage patient discomfort while pacing the heart of apatient at a variable rate and a fixed energy. Variable rate and fixedenergy pacing may be appropriate in response to various types of cardiacarrhythmias, including a bradycardia (i.e., an excessively slow heartrate below 40 beats per minute), tachycardia (i.e., an excessively fastheart rate), an erratic heart rate with no discernible regular sinusrhythm, a lack of sensed cardiac activity (asystole), and pulselesselectrical activity. Some of these cardiac arrhythmias may occurfollowing one or more defibrillation shocks.

As known to those skilled in the art, pacing at a fixed rate and energymay not be appropriate for the particular type of cardiac arrhythmia ofthe patient, and even where the rate and energy level are appropriate,pacing at a fixed rate can result in competition between the rate atwhich the pacing pulses are being applied and the intrinsic rhythm ofthe patient's heart. For example, pacing at a fixed rate may result inthe application of a pacing pulse during the relative refractory periodof the normal cardiac cycle (a type of R wave on a T wave effect) thatcould promote ventricular tachycardia or ventricular fibrillation. Toovercome some of the disadvantages of fixed rate and energy pacing, thetreatment manager can be configured to perform demand pacing, whereinthe rate of the pacing pulses may be varied dependent on thephysiological state of the patient and the patient's current discomfortparameter. For example, during demand pacing, the treatment manager candeliver a pacing pulse only when needed by the patient. In general, whenexecuting in demand mode, the device searches for any intrinsic cardiacactivity of the patient, and if a heartbeat is not detected within adesignated interval, a pacing pulse is delivered and a timer is set tothe designated interval. Where the designated interval expires withoutany detected intrinsic cardiac activity of the patient, another pacingpulse is delivered and the timer reset. In some examples, where anintrinsic heartbeat of the patient is detected within the designatedinterval, the device resets the timer and continues to search forintrinsic cardiac activity.

FIG. 9 helps to illustrate some of the aspects of demand pacing and themanner in which demand pacing can be performed by the treatment manager.As illustrated in FIG. 9, when executing demand pacing, the treatmentmanager may have a variable pacing interval 910 corresponding to therate at which pacing pulses are delivered to the patient in the absenceof any intrinsic cardiac activity as may be detected by the cardiacmonitor. For example, the rate at which pulsing paces are to bedelivered to the patient (referred to as the “base pacing rate” herein)may be set at 60 pulses per minute and therefore, the corresponding basepacing interval 910 would be set to 1 second.

Although the base pacing rate may be set to a particular value based onthe physiological condition of the patient and input from a medicalprofessional, the treatment manager can include a number of differentpacing routines to respond to different cardiac arrhythmias, such asbradycardia, tachycardia, an erratic heart rate with no discernibleregular sinus rhythm, asystole, or pulseless electrical activity. Thesepacing routines may be implemented using a variety of hardware andsoftware components and examples are not limited to a particularconfiguration of hardware or software. For instance, the pacing routinesmay be implemented using an application-specific integrated circuit(ASIC) tailored to perform the functions described herein.

The treatment manager may also have a hysteresis rate (not shown in FIG.9) corresponding to the detected intrinsic heart rate of the patientbelow which the device performs pacing. According to some examples, thehysteresis rate is a configurable parameter that is expressed as apercentage of the patient's intrinsic heart rate. In the above example,the hysteresis rate may correspond to 50 beats per minute. In thisexample, if the intrinsic heart rate of the patient fell to 50 beats perminute or below (e.g., more than approximately 1.2 seconds betweendetected beats), the treatment manager would generate and apply a pacingpulse to the patient.

During application of a pacing pulse to the body of a patient and ashort time thereafter, the treatment manager may intentionally blank outa portion of the ECG signals being received by the ECG monitoring anddetection circuitry (e.g., the electrodes, sensor interface, and cardiacmonitor) to prevent this circuitry, which may include amplifiers, A/Dconverters, etc. from being overwhelmed (e.g., saturated) by the pacingpulse. This may be performed in hardware, software, or a combination ofboth. This period of time, referred to herein as “the blanking interval”920 may vary (e.g., between approximately 30 milliseconds to 200milliseconds), but is typically between approximately 40 milliseconds to80 milliseconds in duration.

In addition to the blanking interval 920, the treatment manager can havea variable refractory period 930 that may vary dependent upon the basepacing rate. The refractory period 930 corresponds to a period of timein which signals sensed by the ECG sensing electrodes are ignored, andmay include the blanking interval. The refractory period 930 allows anygenerated QRS complexes or T waves induced in the patient by virtue ofthe pacing pulse to be ignored, and not interpreted as intrinsic cardiacactivity of the patient. The refractory period can be configured as isdone with VVI implanted pacemakers, e.g., with a single chamber,ventricular sensed, ventricular stimulation pacemakers known to thoseskilled in the art. For example, the refractory period can be aninterval following a paced or sensed event in the chamber containing thepacing or sensing lead, during which the inhibited (SSI) or triggered(SST) pacemaker is not reset. In a VVI pacemaker, a first part of therefractory period is a programmable, absolutely refractory blankingperiod. For example, it prevents a resetting of the pacemaker by asensing of a) post-pacing ventricular potentials, b) the end of the QRS,or c) the T wave. For example, an occurrence of an event during theblanking period may not be visible on the marker channels. For typicalapplications, the refractory period is generally between about 150milliseconds and 400 milliseconds.

In one example, the sensitivity of the ECG monitoring and detection thatis performed by the treatment manager may also be varied to adjust thedegree by which the ECG monitoring and detection circuitry can detectthe patient's intrinsic cardiac activity. For example, where theamplitude of certain discernible portions (e.g., an R-wave) of apatient's intrinsic ECG signal is below that typically encountered, thevoltage threshold over which this discernible portion can be detected asbelonging to an ECG signal (and not attributed to noise or otherfactors) may be lowered, for example from 2.5 millivolts to 1.5millivolts, to better detect the patient's intrinsic cardiac activity.For instance, during an initial fitting of the medical device, thesensitivity threshold of the device may be reduced to a minimal value(e.g., 0.4 millivolts) and the patient's intrinsic ECG signals may bemonitored. The sensitivity threshold may then be incrementally increased(thereby decreasing the sensitivity of the device) and the patient'sintrinsic ECG signals monitored until these ECG signals are no longersensed. The sensitivity threshold may then be incrementally decreased(thereby increasing the sensitivity of the device) until the patient'sintrinsic ECG signals are again sensed, and the sensitivity threshold ofthe device may be set to approximately half this value.

As with fixed energy and rate pacing, the treatment manager may beconfigured during an initial fitting per the act 402 or otherwise toprovide pulses at a fixed energy level and a fixed pulse width inresponse to detection of any of the above-noted events by the cardiacmonitor. The maximum current level of the current waveform may be set toa value between approximately 10 milliamps to 200 milliamps, the pulsewidth may be set to a fixed value between approximately 20 millisecondsto 40 milliseconds, and the base rate of the pulses may be set to afixed value between approximately 30 pulses per minute to approximately200 pulses per minute, although the actual rate of the pacing pulses canvary based upon the intrinsic cardiac activity of the patient. Inaccordance with one example, a 40 millisecond constant current pulse isused, and the current level is set to a fixed value based upon the inputof a medical professional, such as the patient's cardiologist and thephysiological condition of the patient. The base pacing rate and thehysteresis rate may also be set based upon the input of the patient'scardiologist (or other medical professional) and the physiologicalcondition of the patient, and the blanking interval and refractoryperiod set to an appropriate time interval based upon the base pacingrate and/or the hysteresis rate.

FIG. 7 illustrates one example of a managed pacing routine 700 that isexecuted within the act 514. The managed pacing routine 700 executes avariable rate and fixed energy pacing process that is managed todecrease discomfort relative to conventional pacing processes. As shownin FIG. 7, the managed pacing routine 700 includes acts of deliveringpacing pulses, calculating a discomfort parameter, adjusting pacingparameters, and determining whether pacing should continue.

In act 702, the treatment manager delivers one or more pacing pulses tothe patient according to the baseline parameters loaded in the act 512described above with reference to FIG. 5. In examples where the act 512has been omitted, the treatment manager delivers one or more pacingpulses to the patient in accord with default pacing parameters stored inthe data storage. In the act 702, the one or more pacing pulses may bedelivered in conjunction with one or more TENS pulses executed accordingto a TENS routine associated with the pacing routine 700.

In act 704, the discomfort monitor prompts for, receives, and recordsdiscomfort information and records any discomfort information acquiredduring execution of the pacing pulses for subsequent processing. In someexamples, the discomfort information is recorded in the data storage.This discomfort information may be received as voluntary or involuntaryinput from the user via the user interface or may be acquired from oneor more other sensors coupled to a sensor interface. Examples ofdiscomfort information received via the user interface includeutterances (e.g., words, moans, groans, crying, or other expressions)and actuation of a discomfort measuring and/or indicating device (e.g.,strain gauge, button, rotary dial, elastic deformable solid). Forexample, the user can indicate a level of discomfort he or she feels byactuating any of one or more user interface elements as describedherein. Examples of discomfort information received via other sensors(e.g., motion detection sensors, strain gauges in a garment) includemovements (e.g., tensing of muscles, jerking, shuttering, flinching,changes in respiration) and lack of movement.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for theinput by, for example, presenting a discomfort scale via the userinterface. The discomfort scale may include numeric values and the userinterface may request that the user rate the discomfort experienced onthe numeric scale. The discomfort scale may also include graphicalrepresentations (e.g., faces) and the user interface may request thatthe user rate the discomfort experienced on the graphical scale. In someexamples, the discomfort monitor infers the intensity of the discomfortbased on the amount of pressure detected by the user interface or theamount of time a user interface element remains actuated. For example,in a manner similar to that outlined above for the baseline process, thevoluntary input may be in the form of actuation of one or more userinterface elements, such as a force sensor (e.g., piezoelectric, quartz,or ceramic based transducer), a push or squeeze button, a rotaryspring-loaded dial, or an elastic deformable solid.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for a changein input where the input has not changed state for a time period greaterthan a value of a timeout configurable parameter of the medical device.In this way, these examples prevent involuntary input received asvoluntary input from affecting the behavior of the medical device for atime period greater than the timeout.

In the act 706, the discomfort monitor determines whether the pacingpulses delivered in the previous iteration of the act 702 were tolerableto the patient. If the pacing pulses were tolerable, the treatmentmanager proceeds to the act 710. If the pacing pulses were nottolerable, the treatment manager proceeds to the act 708. In someexamples, the discomfort monitor determines whether the pacing pulseswere tolerable at least in part by quantifying discomfort information.This discomfort information quantified by the discomfort monitor mayhave been acquired during execution of the pacing pulses in the act 702or may have been received as voluntary input in response to one or moreprompts provided to the user via the user interface within the act 704(i.e., after execution of the pacing pulses in act 702 is complete). Insome examples, the discomfort monitor assigns a value to the discomfortparameter based on the discomfort information using one or more of themechanisms described herein (e.g., the mechanisms described above withreference to the act 408 of FIG. 4). For instance, the discomfortmonitor may store any of the following values as the value of thediscomfort parameter: a value of a point on the discomfort scaleselected via user input, a value calculated based on an amount ofpressure exerted by the user on an element of the user interface, or avalue calculated based on motion of the patient or some otherinvoluntary reaction to the pacing pulses exhibited by the patient.

In some examples, the discomfort monitor determines whether the pacingpulses were tolerable by comparing the value of the discomfort parameterto a discomfort threshold value. This discomfort threshold value may bea configurable parameter of the medical device. In some examples, thediscomfort monitor determines that the pacing pulses were tolerablewhere the value of the discomfort parameter maintains a predefinedrelationship with to the discomfort threshold value (e.g., where thevalue of the discomfort parameter does not transgress the discomfortthreshold value). In these examples, the discomfort monitor determinesthat the pacing pulses were not tolerable where the value of thediscomfort parameter does not maintain a predefined relationship withthe discomfort threshold value (e.g. where the value of the discomfortparameter is equal to or transgresses the discomfort threshold value).It is appreciated that, depending on the specific calculations used, adiscomfort threshold value may be transgressed by a value that isgreater than or less than the discomfort threshold value.

In act 708, the discomfort monitor adjusts the pacing parameters. Insome examples, the discomfort monitor determines the adjusted pacingparameters substantially in real time based on immediate feedback fromthe patient as described above with reference to FIG. 16.

In some examples, where voluntary feedback is unavailable (e.g., thepatient is unable to provide dynamic feedback regarding his or her levelof discomfort) the discomfort monitor determines the adjusted pacingparameters in a similar manner as outlined above with respect to thebaseline process 400 by solving an optimization problem similar to theoptimization problem described above with reference to described abovewith reference to act 412 of FIG. 4. However, the optimization problemsolved within the act 708 replaces the these constraints:

15 milliamps≤a_(i)≤200 milliamps;

0.5 milliseconds≤w_(i)≤40 milliseconds; and

20 pacing pulses per minute≤r_(i)≤200 pacing pulses per minute; with thefollowing constraints:

a_(i)=a_(b) (or the value of a configurable parameter set for demandpacing);

w_(i)=w_(b) (or the value of a configurable parameter set for demandpacing); and

r_(i)≥hysteresis rate. In addition, the discomfort monitor improves anyapproximation of the function d(i) by incorporating the data point(s)generated in act 706.

In act 710, the treatment manager receives (via the one or moreelectrodes) and analyzes (via the cardiac monitor) electrode signalsgenerated from detectable characteristics of the patient's cardiacfunction. The cardiac monitor determines whether the patient's currentcardiac condition warrants further pacing. If so, the treatment managerreturns to the act 702 and continues execution of the pacing routine700. If the cardiac monitor determines that the patient's currentcardiac condition does not warrant further pacing (e.g., determineswhether a normal sinus rhythm has returned), the pacing routine 700ends. In some examples, upon termination of the pacing routine 700, thetreatment manager returns to the process 500 and continues to monitorthe patient's physiological signals, such as the patient's ECG,temperature, pulse oxygen level, respiration, etc.

Processes in accord with the managed pacing routine 700 enable patientsto control parameters of pacing routines via feedback provided to a userinterface, thereby enabling patients to actively manage discomfortassociated with external pacing processes.

Demand Pacing—Bradycardia

As discussed above, where bardycardia is detected and the intrinsiccardiac rate of the patient is below that of the hysteresis rate, thetreatment manager will pace the patient at the pre-set base pacing rateand manage the patient's discomfort by executing the pacing routineprocess 700. During this time, the device will continue to monitor thepatient's intrinsic heart rate and will withhold pacing pulses in theevent that an intrinsic heartbeat is detected within designated intervalcorresponding to the hysteresis rate. This type of on demand pacing isfrequently termed “maintenance pacing.”

Demand Pacing—Tachycardia

For responding to tachycardia, the treatment manager may additionallyinclude another pacing rate, referred to as an “anti-tachyarrhythmicpacing rate” herein, above which the treatment manager will identifythat the patient is suffering from tachycardia, and will pace thepatient in a manner to bring the patient's intrinsic heart back towardthe base pacing rate and manage the patient's discomfort by executingthe pacing routine process 700. For example, the treatment manager mayemploy a technique known as overdrive pacing wherein a series of pacingpulses (e.g., between about 5 and 10 pacing pulses) are delivered to thepatient at a rate above the intrinsic rate of the patient in an effortto gain control of the patient's heart rate. Once it is determined thatthe treatment manager is in control of the patient's heart rate, therate of the pulses may be decremented, for example by about 10milliseconds, and another series of pacing pulses delivered. Thisdelivery of pulses and the decrease in frequency may continue until thedetected intrinsic cardiac rate of the patient is below theanti-tachyarrhythmic pacing rate. This type of pacing is frequentlytermed “overdrive pacing” or “fast pacing.”

Demand Pacing—Erratic Heart Rate

For responding to an erratic heart rate, the treatment manager mayperform a type of pacing that is similar to a combination of maintenancepacing and overdrive pacing discussed above. For example, where thetreatment manager detects an erratic heart rate with no discerniblesinus rhythm, the treatment manager may deliver a series of pacingpulses (e.g., between about 5 and 10 pacing pulses) to the patient at aparticular rate, while managing the patient's discomfort in accord withthe pacing routine 700. This rate may be one that is above a lower rateof a series of detected intrinsic beats of the patient's heart and belowan upper rate of the detected intrinsic beats of the patient's heart.After delivering the series of pulses, the treatment manager may monitorthe patient's heart to determine if it has synchronized to the rate ofthe series of delivered pulses. Where the intrinsic rate of thepatient's heart is still erratic, the treatment manager may increase therate of the series of pulses and deliver another series. This maycontinue until it is established that the patient's heart assumes a moreregular state. Upon determining that the patient's heart is in a moreregular state, the treatment manager may perform maintenance pacing ifit is determined that the patient's intrinsic heart rate is too low asdiscussed in the “Demand Pacing—Bradycardia” section above, or performpacing at a decremented rate in the manner discussed in “DemandPacing—Tachycardia” section above, if such is warranted.

Demand Pacing—Asystole or Pulseless Electrical Activity

For responding to asystole or a detected condition of pulselesselectrical activity, the treatment manager may perform maintenancepacing similar to that described in the “Demand Pacing—Bradycardia”section above and manage patient discomfort by executing the pacingroutine 700. This type of pacing would be performed after a series ofone or more defibrillating shocks that attempt to restore a normal sinusrhythm to the heart of the patient.

In each of the types of pacing described above, the treatment managermay be configured to perform a particular type of pacing only after aprogrammable delay after such cardiac arrhythmias are detected, or aftera programmable period of time after one or more defibrillating shocksare delivered.

Capture Management

In one example of the act 514, the treatment manager is configured tomanage patient discomfort while pacing the heart of a patient usingcapture management with an adjustable energy level and an adjustablerate in response to various types of cardiac arrhythmias. The varioustypes of cardiac arrhythmias can include a bradycardia, tachycardia, anerratic heart rate with no discernible regular sinus rhythm, a lack ofsensed cardiac activity (asystole) following or independent of one ormore defibrillation shocks, a life-threatening bradycardia following oneor more defibrillation shocks, or pulseless electrical activityfollowing one or more defibrillation shocks.

As known to those skilled in the art, capture management refers to atype of pacing in which the energy level of pacing pulses and the rateof delivery of those pacing pulses may be varied based upon the detectedintrinsic activity level of the patient's heart and the detectedresponse of the patient's heart to those pacing pulses. In cardiacpacing, the term “capture” is used to refer to the response of apatient's heart to a pulse of energy which results in ventriculardepolarization. In cardiac pacing, it is desirable to limit the amountof energy in each pulse to a minimal amount required for capture;thereby decreasing the amount of discomfort associated with externalpacing.

In general, the manner in which the treatment manager performs capturemanagement pacing is similar to that of demand pacing described above,in that it may adjust the rate at which pacing pulses are deliveredbased upon the detected intrinsic rate of cardiac activity of thepatient and, potentially, based on the a level of discomfort beingexperienced by the patient. The sensitivity of the device to thepatient's ECG may be adjusted in a similar manner to that describedabove with respect to demand pacing. Further, capture management pacingmay be used to treat the same types of cardiac arrhythmias as the demandpacing described above, such as bradycardia, tachycardia, an erraticheart rate with no discernible sinus rhythm, asystole, or pulselesselectrical activity.

However, in contrast to a medical device that performs demand pacing, amedical device that is configured to perform capture management pacingwill typically have a refractory period 930 (see FIG. 9) that issignificantly shorter than a device configured to perform demand pacing.Indeed, when using capture management pacing, there may be no refractoryperiod 930 at all, but only a blanking interval 920. In some examples,where there is a refractory period 930, the refractory period 930 may besimilar in duration to the blanking interval 920. As would beappreciated by those skilled in the art, this is because during capturemanagement pacing, the response of the patient's heart is monitored todetect whether the delivered pulse of energy resulted in capture.

During capture management pacing, the treatment manager can initiallydeliver a pulse of energy at a predetermined, low energy level andmonitor the patient's response to determine if capture resulted. Whereit is determined that the delivered pulse did not result in capture, theenergy level of the next pulse may be increased. For example, where thetreatment manager resides in a medical device that is external to thepatient, the initial setting may be configured to provide a 40milliseconds rectilinear and constant current pulse of energy at acurrent of 40 milliamps, and increase the amount of current inincrements of 2 milliamps until capture results. The next pacing pulsemay be delivered at increased current relative to the first pacing pulseand at a desired rate relative to the first pacing pulse in the absenceof any detected intrinsic cardiac activity of the patient or intolerablediscomfort to the patient. Where the next pacing pulse does not resultin capture, the energy may be increased until capture is detected. Thetreatment manager may then continue pacing at this energy level and at adesired rate in the absence of any detected intrinsic cardiac activityof the patient or intolerable discomfort to the patient. During thisperiod of time, the treatment manager monitors the patient's cardiacresponse to the pacing pulses, and may increment the energy levelfurther, should it be determined over one or more subsequent pulses thatcapture did not result. Similarly, during this period, the discomfortmonitor tracks the patient's discomfort parameter and may adjust one ormore pacing parameters in response to determining that the patient'sdiscomfort parameter has, for example, transgressed a discomfortthreshold value.

In one example, the treatment manager may apply a series of pulses at aninitial energy level and rate, and monitor the patient's response todetermine if capture resulted. Where capture did not result, or wherecapture resulted in response to some of the pulses, but not all, thetreatment manager may increase the energy of a next series of pulsesuntil capture results for each pulse.

In some examples, the treatment manager may be configured to identify aminimum amount of energy that results in capture during capturemanagement pacing. Where it is determined that the delivered pulse didresult in capture, the energy level of the next pulse may be decreased.For example, where the treatment manager resides in a medical devicethat is external to the patient, the initial setting may be configuredto provide a 40 milliseconds constant current pulse of energy at acurrent of 70 milliamps. Where it is determined that the delivered pulseresulted in capture, subsequent pacing pulse may be delivered atdecreased in increments of 5 milliamps (or more where the discomfortparameter value exceeds the discomfort threshold value) and at a desiredrate relative to the first pacing pulse in the absence of any detectedintrinsic cardiac activity of the patient until capture is no longerachieved or until the discomfort parameter of the patient transgress thediscomfort threshold value. Where the next pacing pulse does not resultin capture, the energy setting may be increased to the last currentknown to produce a pulse resulting in capture, and then delivering apulse at the higher energy setting, thus delivering the minimal amountof energy required for capture. The treatment manager may then continuepacing at this energy level and at a desired rate in the absence of anydetected intrinsic cardiac activity of the patient or intolerablediscomfort to the patient. During this period of time, a similar routinemay be re-performed at predetermined intervals to ensure that theminimum amount of energy is being delivered for capture. In addition,during this period of time, the treatment manager monitors the patient'scardiac response to the pacing pulses, and may increase the energy levelshould it be determined over one or more subsequent pulses that capturedid not result.

FIG. 8 illustrates one example of a managed pacing routine 800 that isexecuted within the act 514. The managed pacing routine 800 executes acapture management pacing process that is managed to decrease discomfortrelative to conventional pacing processes. As shown in FIG. 8, themanaged pacing routine 800 includes acts of delivering pacing pulses,receiving and analyzing ECG signals, determining whether captureoccurred, calculating a discomfort parameter, determining whether thediscomfort caused by the pacing routine 800 is intolerable, adjustingpacing parameters, and determining whether pacing should continue.

In act 802, the treatment manager delivers one or more pacing pulses tothe patient according to the baseline parameters loaded in the act 512described above with reference to FIG. 5. In examples where the act 512has been omitted, the treatment manager delivers one or more pacingpulses to the patient in accord with default pacing parameters stored inthe data storage. In at least one example, the default pacing parametervalues are each set at the maximum of each range.

In the act 802, the one or more pacing pulses may be delivered inconjunction with one or more TENS pulses executed according to a TENSroutine associated with the pacing routine 800. In at least someexamples, the TENS pulses are delivered between pacing pulses todistract the patient and decrease the discomfort of the pacing routine800.

In act 804, the treatment manager receives (via the one or moreelectrodes) and analyzes (via the cardiac monitor) electrode signalsgenerated from detectable characteristics of the patient's cardiacfunction. In act 806, the cardiac monitor determines whether delivery ofthe one or more pacing pulses resulted in capture or improved cardiacfunction. The cardiac monitor may make this determination by analyzingprocessed electrode data to determine whether a normal heart beatresulted from one of the one or more pacing pulses. The cardiac monitormay also make this determination by analyzing processed acoustic datafrom an acoustic sensor included in the medical device as disclosed inU.S. Patent Application Publication No. US2015/0005588, titled“THERAPEUTIC DEVICE INCLUDING ACOUSTIC SENSOR” and published Jan. 1,2015, which is hereby incorporated herein by reference in its entirety.For instance, the cardiac monitor may infer capture from detection ofthe S1 and S2 heart sounds proximal to delivery of the pacing pulse.

In some examples of the act 806, the cardiac monitor does not infercapture has occurred until the patient's heart rate is equal to ortransgresses the patient's hysteresis rate for a predetermined period(e.g., 6 seconds or 5 heartbeats). If delivery of the one or more pacingpulses did not result in capture, the treatment manager proceeds to act812.

In act 808, the discomfort monitor prompts for, receives, and recordsdiscomfort information and records any discomfort information acquiredduring execution of the pacing pulses for subsequent processing. In someexamples, the discomfort information is recorded in the data storage.This discomfort information may be received as voluntary or involuntaryinput from the user via the user interface or may be acquired from oneor more other sensors coupled to a sensor interface. Examples ofdiscomfort information received via the user interface includeutterances (e.g., words, moans, groans, crying, or other expressions)and actuation of a discomfort measuring and/or indicating device (e.g.,strain gauge, button, rotary dial, elastic deformable solid). Forexample, the user can indicate a level of discomfort he or she feels byactuating any of one or more user interface elements as describedherein. Examples of discomfort information received via other sensors(e.g., motion detection sensors, strain gauges in a garment) includemovements (e.g., tensing of muscles, jerking, shuttering, flinching,changes in respiration) and lack of movement.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for theinput by, for example, presenting a discomfort scale via the userinterface. The discomfort scale may include numeric values and the userinterface may request that the user rate the discomfort experienced onthe numeric scale. The discomfort scale may also include graphicalrepresentations (e.g., faces) and the user interface may request thatthe user rate the discomfort experienced on the graphical scale. In someexamples, the discomfort monitor infers the intensity of the discomfortbased on the amount of pressure detected by the user interface or theamount of time a user interface element remains actuated. For example,in a manner similar to that outlined above for the baseline process, thevoluntary input may be in the form of actuation of one or more userinterface elements, such as a force sensor (e.g., piezoelectric, quartz,or ceramic based transducer), a push or squeeze button, a rotaryspring-loaded dial, or an elastic deformable solid.

In some examples where the discomfort information is received asvoluntary input, the discomfort monitor may prompt the user for a changein input where the input has not changed state for a time period greaterthan a value of a timeout configurable parameter of the medical device.In this way, these examples prevent involuntary input received asvoluntary input from affecting the behavior of the medical device for atime period greater than the timeout.

In the act 810, the discomfort monitor determines whether the pacingpulses delivered in the previous iteration of the act 802 were tolerableto the patient. If the pacing pulses were tolerable, the treatmentmanager proceeds to the act 810. If the pacing pulses were nottolerable, the treatment manager proceeds to the act 808. In someexamples, the discomfort monitor determines whether the pacing pulseswere tolerable at least in part by quantifying discomfort information.This discomfort information quantified by the discomfort monitor mayhave been acquired during execution of the pacing pulses in the act 802or may have been received as voluntary input in response to one or moreprompts provided to the user via the user interface within the act 808(i.e., after execution of the pacing pulses in act 802 is complete). Insome examples, the discomfort monitor assigns a value to the discomfortparameter based on the discomfort information using one or more of themechanisms described herein (e.g., the mechanisms described above withreference to the act 408 of FIG. 4). For instance, the discomfortmonitor may store any of the following values as the value of thediscomfort parameter: a value of a point on the discomfort scaleselected via user input, a value calculated based on an amount ofpressure exerted by the user on an element of the user interface, or avalue calculated based on motion of the patient or some otherinvoluntary reaction to the pacing pulses exhibited by the patient.

In some examples, the discomfort monitor determines whether the pacingpulses were tolerable by comparing the value of the discomfort parameterto a discomfort threshold value. This discomfort threshold value may bea configurable parameter of the medical device. In some examples, thediscomfort monitor determines that the pacing pulses were tolerablewhere the value of the discomfort parameter maintains a predefinedrelationship with to the discomfort threshold value (e.g., where thevalue of the discomfort parameter does not transgress the discomfortthreshold value). In these examples, the discomfort monitor determinesthat the pacing pulses were not tolerable where the value of thediscomfort parameter does not maintain a predefined relationship withthe discomfort threshold value (e.g. where the value of the discomfortparameter is equal to or transgresses the discomfort threshold value).It is appreciated that, depending on the specific calculations used, adiscomfort threshold value may be transgressed by a value that isgreater than or less than the discomfort threshold value.

In act 808, the discomfort monitor adjusts the pacing parameters. Insome examples, the discomfort monitor determines the adjusted pacingparameters substantially in real time based on immediate feedback fromthe patient as described above with reference to FIG. 16.

In some examples, where voluntary feedback is unavailable (e.g., thepatient is unable to provide dynamic feedback regarding his or her levelof discomfort) the discomfort monitor determines the adjusted pacingparameters in a similar manner as outlined above with respect to thebaseline process 400 by solving an optimization problem similar to theoptimization problem described above with reference to described abovewith reference to act 412 of FIG. 4. However, the optimization problemsolved within the act 812 replaces at least one of the theseconstraints:

15 milliamps≤a_(i)≤200 milliamps;

0.5 milliseconds≤w_(i)≤40 milliseconds;

20 pacing pulses per minute≤r_(i)≤200 pacing pulses per minute;

20 microseconds≤p_(i)≤500 microseconds;

10 percent≤d_(i)≤100 percent; and

40 microseconds≤c_(i)≤100 microseconds;

with a corresponding one of these following constraints:

a_(i)≥a_(i−1);

w_(i)≥w_(i−1);

r_(i)≥r_(i−1);

p_(i)≥p_(i−1);

d_(i)≥d_(i−1); and

c_(i)≥c_(i−1). In addition, the discomfort monitor improves anyapproximation of the function d(i) by incorporating the data point(s)generated in act 810.

In some examples, where the patient is not actively contributingdiscomfort information (e.g., the patent is unconscious), the treatmentmanager adjusts the pacing parameters to increase the efficacy of thepacing pulses as described above, for instance, by increasing thecurrent by 2 milliamps. In some examples, wherein the patient is notactively contributing discomfort information, the treatment managerdetermines the adjusted pacing parameters by solving an optimizationproblem similar to the optimization problem described above withreference to described above with reference to act 412 of FIG. 4.However, the optimization problem solved within the at 812 replaces atleast one of the these constraints:

15 milliamps≤a_(i)≤200 milliamps;

0.5 milliseconds≤w_(i)≤40 milliseconds;

20 pacing pulses per minute≤r_(i)≤200 pacing pulses per minute;

20 microseconds≤p_(i)≤500 microseconds;

10 percent≤d_(i)≤100 percent; and

40 microseconds≤c_(i)≤100 microseconds;

with a corresponding one of these following constraints:

a_(i)≤a_(i−1);

w_(i)≤w_(i−1);

r_(i)≤r_(i−1);

p_(i)≤p_(i−1);

d_(i)≤d_(i−1); and

c_(i)≤c_(i−1). In addition, the discomfort monitor improves anyapproximation of the function d(i) by incorporating the data point(s)generated in act 810.

In act 814, the treatment manager receives (via the one or moreelectrodes) and analyzes (via the cardiac monitor) electrode signalsgenerated from detectable characteristics of the patient's cardiacfunction. During the analysis, the cardiac monitor determines whetherthe patient's current cardiac condition warrants further pacing. If so,the treatment manager returns to the act 802 and continues execution ofthe pacing routine 800. If the cardiac monitor determines that thepatient's current cardiac condition does not warrant further pacing(e.g., determines whether a normal sinus rhythm has returned), thepacing routine 800 ends. In some examples, upon termination of thepacing routine 800, the treatment manager returns to the process 500 andcontinues to monitor the patient's physiological signals, such as thepatient's ECG, temperature, pulse oxygen level, respiration, etc.

Processes in accord with the managed pacing routine 800 enable patientsto control parameters of pacing routines via feedback provided to a userinterface, thereby enabling patients to actively manage discomfortassociated with external pacing processes.

It should be appreciated that in the various examples described above,an medical device has been described which may not only providelife-saving defibrillation or cardioversion therapy, but may alsoprovide a wide variety of different pacing regimens. Because the medicaldevice can monitor a patient's intrinsic cardiac activity, the patient'sthoracic impedance, and other physiological characteristics of thepatient, the medical device may be configured to recommend varioussettings to a medical professional for review and approval. The varioussettings that may be recommended may include a recommended base pacingrate, a recommended hysteresis rate, a recommended anti-tachyarrhythmicpacing rate, a recommended energy level (or initial energy level ifcapture management is used), a recommended blanking interval, and/orrefractory period, and a recommended sensitivity threshold. In the caseof a pacing device such as the LifeVest® cardioverter defibrillator,this initial recommendation may be performed when the patient is beingfitted for and trained on the use of the medical device.

Although the ability to recommend such settings to a medicalprofessional for their review and approval is particularly well suitedto a LifeVest® cardioverter defibrillator, such functionality could alsobe implemented in an Automated External Defibrillator (AED) or anAdvanced Life Support (ALS) type of defibrillator, such as the M Seriesdefibrillator, R Series ALS defibrillator, R Series Plus defibrillator,or E Series defibrillator manufactured by the ZOLL Medical Corporationof Chelmsford Mass. It should be appreciated that monitoring thepatient's intrinsic cardiac activity and other physiologicalcharacteristics and making recommendations to a trained medicalprofessional for their review and approval (or possible modification)could reduce the amount of time that is spent manually configuring suchdevices prior to use on the patient.

Each of the processes described herein depict one particular sequence ofacts in a particular embodiment. The acts included in these processesmay be performed by, or using, one or more computer systems speciallyconfigured as discussed herein. Some acts are optional and, as such, maybe omitted in accord with one or more embodiments. Additionally, theorder of acts can be altered, or other acts can be added, withoutdeparting from the scope of the embodiments described herein.

Having thus described several aspects of at least one example of thisdisclosure, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the scope of thedisclosure. Accordingly, the foregoing description and drawings are byway of example only.

What is claimed is:
 1. An external medical device comprising: at leastone therapy electrode configured to be disposed on a patient; and atreatment manager, coupled to the at least one therapy electrode,configured to execute a baseline process to determine at least one of arange of values for a discomfort parameter corresponding to at least onepacing routine and a patient discomfort threshold value corresponding tothe at least one pacing routine, detect a cardiac condition of thepatient, execute the at least one pacing routine, the at least onepacing routine being associated with the cardiac condition, monitor thediscomfort parameter associated with the patient during execution of theat least one pacing routine, determine whether the discomfort parametertransgresses the at least one of the range of values and the patientdiscomfort threshold value, and adjust at least one characteristic ofthe at least one pacing routine in response to determining that thediscomfort parameter transgresses the at least one of the range ofvalues and the patient discomfort threshold value.
 2. The device ofclaim 1, further comprising a user interface for receiving discomfortinformation regarding the patient in connection with the at least onepacing routine.
 3. The device of claim 2, wherein the treatment manageris configured to receive the discomfort information regarding thepatient responsive to selection of an element of the user interface. 4.The device of claim 3, wherein the user interface displays a discomfortscale and the element includes a selectable point on the discomfortscale.
 5. The device of claim 4, wherein the discomfort scale is atleast one of numeric and image-based.
 6. The device of claim 4, whereinthe user interface includes a touch screen configured to display aplurality of selectable points on the discomfort scale.
 7. The device ofclaim 3, wherein the selection includes at least one of a touch and anutterance.
 8. The device of claim 7, wherein the utterance includes atleast one predefined word.
 9. The device of claim 3, wherein thetreatment manager is further configured to: detect, via a touchdetector, a touch having a duration; and determine whether thediscomfort parameter transgresses the patient discomfort threshold valuebased on the duration.
 10. The device of claim 2, wherein the discomfortparameter is based on at least one of the discomfort informationreceived from a user via the user interface and informationautomatically detected by at least one sensor distinct from the userinterface.
 11. The device of claim 10, wherein the user interfacecomprises at least one of a touch screen, a button, a microphone forreceiving audible commands, a strain gauge, a force sensor, apiezoelectric transducer, and a rotating spring-loaded dial.
 12. Thedevice of claim 10, wherein the treatment manager is configured toreceive the discomfort information descriptive of the discomfortparameter with reference to an amount of pressure exerted by the user onan element of the user interface.
 13. The device of claim 12, whereinthe treatment manager is configured to determine a present value of thediscomfort parameter during execution of the at least one pacing routinebased on at least one of an amount of pressure detected by the userinterface and a duration of time the element of the user interfaceremains actuated.
 14. The device of claim 12, wherein the element of theuser interface is at least one of a quartz sensor, a ceramic forcesensor, and a piezoelectric transducer.
 15. The device of claim 10,wherein the user interface comprises a force sensor configured to detecta force applied by the user squeezing at least one surface of the forcesensor.
 16. The device of claim 10, wherein the at least one sensorincludes at least one of a motion sensor, an audio sensor, aphysiological sensor, an electrode, an accelerometer, and a bloodpressure sensor.
 17. The device of claim 1, wherein the treatmentmanager is further configured to adjust at least one characteristic ofthe at least one pacing routine in response to determining that a valueof the discomfort parameter is equal to or transgresses the patientdiscomfort threshold value.
 18. The device of claim 17, wherein the atleast one characteristic of the at least one pacing routine includes atleast one of an amplitude of pacing pulses, a width of the pacingpulses, a rate of the pacing pulses, a waveform of the pacing pulses, aperiod of the pacing pulses, a duty cycle of the pacing pulses, and aramp time constant of the pacing pulses.
 19. The device of claim 1,wherein the cardiac condition comprises at least one of bradycardia,tachycardia, asystole, pulseless electrical activity, and erratic heartrate.
 20. The device of claim 1, wherein the at least one pacing routinecomprises at least one of fixed rate pacing, fixed energy pacing,adjustable rate pacing, and capture management pacing.
 21. The device ofclaim 1, wherein the discomfort parameter is indicative of a level ofdiscomfort experienced by the patient during the at least one pacingroutine.
 22. The device of claim 1, wherein the treatment manager isconfigured to execute the baseline process during an initial fitting ofthe external medical device to the patient.
 23. The device of claim 1,wherein the treatment manager is further configured to optimize at leastone characteristic of the at least one pacing routine in response to thedetermination that the discomfort parameter transgresses the at leastone of the range of values and the patient discomfort value.
 24. Thedevice of claim 23, wherein the treatment manager is configured tooptimize the at least one characteristic along a scale selected from atleast one of a linear scale, a logarithmic scale, and an exponentialscale.
 25. The device of claim 23, wherein the treatment manager isconfigured to optimize the at least one characteristic at least in partby executing a regression analysis using historical values of the atleast one characteristic.
 26. The device of claim 1, wherein thetreatment manager is further configured to adjust the patient discomfortthreshold value based on the patient's state of consciousness.
 27. Thedevice of claim 1, further comprising a transcutaneous electrical nervestimulation unit configured to provide background stimulation to thepatient during execution of the at least one pacing routine.
 28. Thedevice of claim 1, wherein executing the baseline process furthercomprises setting the at least one characteristic of the at least onepacing routine to an appropriate level based on a physiologicalcondition of the patient.
 29. The device of claim 28, wherein theappropriate level is determined based on typical impedance values for anadult or child.
 30. The device of claim 1, wherein executing thebaseline process further comprises setting the at least onecharacteristic of the at least one pacing routine with reference topacing parameter baselines associated with multiple patients.
 31. Amethod of controlling discomfort of a patient during pacing by anexternal medical device, the method comprising: determining, during abaseline process, at least one of a range of values for a discomfortparameter corresponding to at least one pacing routine of the externalmedical device and a patient discomfort threshold value corresponding tothe at least one pacing routine; detecting a cardiac condition of thepatient, the cardiac condition being associated with the at least onepacing routine; executing the at least one pacing routine; monitoringthe discomfort parameter of the patient during execution of the at leastone pacing routine; and adjusting, responsive to the discomfortparameter transgressing the at least one of the range of values and thepatient discomfort threshold value, at least one characteristic of theat least one pacing routine.
 32. The method of claim 31, furthercomprising receiving, via a user interface, discomfort informationregarding the patient in connection with the at least one pacingroutine.
 33. The method of claim 32, wherein the discomfort parameter isbased on at least one of the discomfort information received from a uservia the user interface and information automatically detected by atleast one sensor distinct from the user interface.
 34. The method ofclaim 33, further comprising receiving the discomfort information from auser selection of an element of the user interface.
 35. The method ofclaim 33, wherein the user interface comprises a touch sensor, themethod further comprising: detecting, via the touch sensor, a touchhaving a duration; and determining whether the discomfort parameter isequal to or transgresses the patient discomfort threshold value withreference to the duration.
 36. The method of claim 31, wherein executingthe baseline process further comprises setting the at least onecharacteristic of the at least one pacing routine to an appropriatelevel based on at least one of a physiological condition of the patient,typical impedance values for an adult or child, and pacing parameterbaselines associated with multiple patients.
 37. A bodily-attachedambulatory medical device comprising: at least one therapy electrodeconfigured to be disposed on a patient; and a treatment manager, coupledto the at least one therapy electrode, configured to execute a baselineprocess to determine at least one of a range of values for a discomfortparameter corresponding to at least one pacing routine and a patientdiscomfort threshold value corresponding to the at least one pacingroutine, detect a cardiac condition of the patient, and execute the atleast one pacing routine, the at least one pacing routine beingassociated with the cardiac condition and having at least onecharacteristic configured for the patient's tolerance for discomfortbased on the at least one of the range of values for the discomfortparameter and the patient discomfort threshold value.